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Paul Danner
Sixth Edit io n
Introduction
Hello, my name is Paul Danner. I am an ASE Ll certified master technician with 20 years of field
experience in driveability diagnostics and computer systems troubleshooting. For the past 11 years I have
been an instructor for Rosedale Technical Institute near Pittsburgh, PA where I developed this book for
training my students. Before entering my class students are expected to have a basic understanding of the 4
stroke engine and also some basic electrical background . Although this is important, it is not completely
necessary to understand most of the topics and testing methods taught in this book.
One of the main focuses in this book is what I like to call the "anti-flowchart". I hate engineer written
flow charts! These are step by step procedures that some pencil pusher thinks is the best way to troubleshoot
a particular problem on a car. For the most part they don't give us technicians enough credit. They are
certainly never written with speed in mind . How could they be when half of them start off with disconnecting
the computer and the sensor and checking the wire for opens and shorts? Do they realize that step one could
take more than a half hour to just get to the computer? This is ridiculous! There has to be a better way! I think
I have said that to myself thousands of times over the past 20 years.
Well guess what, I have found a better way and I want to share it with you. Some of my methods are a
little unorthodox, but if used correctly there is no faster or more accurate method for computer systems
trouble shooting than what I have outlined in this book. Do I still use engineer written flow charts? Of course,
but only as a guide and almost never literally. Maybe someday engineers will wake up and figure out that
some of us can handle more information than what they are providing. Until then we must develop a more
complete understanding of sensors and circuit designs. Once we have these fundamentals we will be able to
troubleshoot ANY computer controlled system, not just a fuel injection computer. I even fixed my furnace at
home using these same principles!
Table of Contents
Universal Testing Methods
SVl'itch Inputs
Transistor Drivers and Output Solenoids
Oxygen Sensor Introduction
Oxygen Sensor Testing
Thern1istors
Potentiometers
Pressure Sensors
The 5 Volt Reference Circuit
Signal Circuit Integrity T esting
Substituted Values
A.irOow Sensors
Types of Fuel Injection
Fuel Delivery Designs
Fuel Pun1p Electrical Circuits
Fuel Pressure Testing
Fuel Injector Driver Designs
Fuel Injector Testing
No Injector Pulse, No Start Problems
Idle Speed Controls
Ignition Systen1 inputs
No Start, No Spark l'roblen1s
No Start, Good Spark and Injector Pulse Condition
EGR System Problen1s
Con1n1on Tern1s and Abbreviations
Section l
Section 2
Section 3
Section 4
Section 5
Sl-'Ction 6
Section 7
Section 8
Section 9
Section 10
Sl-'Ction 11
Sl-'Ction 12
Section 13
Section 14
Section 15
Sl-'Ction 16
Section 17
Section 18
Section 19
Section 20
Sl-'Ction 21
Sl-'Ction 22
Section 23
Section 24
Section 25
1- 29
1 -30
1 - 30
1 - 21
1-27
1-17
1 - 15
1 - 10
1-6
1-7
1-6
1- 17
1 -8
1 -9
1 - 19
1- 16
1 -7
1 - 26
1 -5
1- 29
1-33
1- 26
1 -2
1 -8
1-2
Universal Testing Methods
Section 1
Where Do I Start?
•
•
•
•
•
Fuel
- Is the engine running rich or lean?
- Is there enough fuel delivery under a load?
Ignition
- What is causi ng the misfire?
• Is it lack of spark, fuel or compression?
- What are some quick tests to identify the cause of the misfire?
Mechanical
- Is there a compression problem?
- Is there a jumped timing belt/chain?
- Is there a vacuum leak?
Electrical
- Is there a bad diode in the alternator?
- What is the computers response to low battery voltage?
Emissions
- Is the EGR va lve stuck open?
- Is the exhaust restricted?
- Could the air pump or evap. system be causing problems?
2
•
•
•
•
•
•
Question customer.
Test drive to verify customer complaint. The symptom must be duplicated for an
accurate diagnosis.
Scan for diagnostic trouble codes. (DTCs)
- Check freeze frame data (if available) to determine the engine load and
temperature set by the fault code.
Check for technical service bulletins (TSBs)
RESEARCH!!!
You must know the description and operation of the system or component
before diagnosis begins. (*The main resources I use as an aftermarket
technician: Shop Key, Mitchell, iATN.net, Snap-on's Troubleshooter and the
Component Meter of the Vantage Pro)
•
Find the specific fault code and read or print the step by step "flow
chart". Even if you don't follow it completely you will still gather valuable
information about why the code is set and what the possible causes are.
•
Print the wiring diagram for the system you are troubleshooting.
•
Research theory and operation of the components being tested.
Never forget to perform a visual inspection. This can save you significant time if you
just take a look first!
3
Fuel trim
•
Short term fuel trim is used to keep the 02 sensor moving slightly rich I lean from
stoichiometric. This provides the catalytic converter w ith the necessary gases to properly
reduce the maj or pollutants.
•
Long term fuel trim is learned from the short term fuel trim. Its primary functions are:
-
To keep the short term with as much correction capability as possible. This is achieved
by keeping the short term close to 0°/o.
-
To reta in fuel trim corrections in memory
•
Use the long term fuel trim values to determine if the engine is delivering fuel normally or if it
is correcting for an overly rich or lean condition. Keep in mind that every load/rpm combination
will have a different "learned" long term fuel trim numbers.
•
Positive numbers (numbers above Oo/o) mean the computer is adding fuel. This is a rich
command in response to a lean condition .
•
Negative numbers (numbers below 0%) mean the computer is subtracting fuel. This is a lean
command in response to a rich condition.
•
Oxygen sensor malfunctions w ill cause the computer to add or subtract a disproportionate
amount of fuel. If the 02 sensor voltage is fixed lean (below 450mv), the computer w ill
severely richen the mixture. This will result in poor gas mileage, black smoke and poor low
rpm performance. If the 02 sensor voltage is fixed rich (above 450mv), the computer will
severely lean-out the mixture. This will result in low power and hesitation problems. In either
case the eng ine will run good cold and at wide open throttle (WOT) because the 02 sensor is
not used du ring these times .
4
Understanding ST/L TFT
•
STFT (short term fuel trim)
- #1 job is to keep 02 sensor near (a
little above/below) stoichiometric
is a command from the PCM to alter
injector pulse
- Oo/o = no fuel corrections from factory
preset value
is only used in closed loop
L TFT (long term fuel trim)
- #1 job is to keep STFT as close to 0°/o as
.possible and to retain any fuel corrections
1n memory.
PCM "looks" at L TFT first to know where
to start injector pulse width
learns from STFT%
is a command from the PCM to alter
injector pulse
0°/o = no fuel corrections from factory
preset value
+/- 10 °/o is considered normal on most
systems
may be used in both open and closed loop
•
NOTE* With left and right bank upstream
02 sensors , the PCM uses left and right
bank STFT & L TFT (individual bank fuel
trim control)
Total fuel trim is the sum of the LTFT and STFT
Pre-OBDll GM used Block Learn
(LTFT) and Integrator (STFT)
binary numbers. 128 = 0°/o
; NORMAL :
: RANGE :
_G
__
F_U_EL
--.~· ~ 12s ~--~-A
-D
_D
_l_
N_
G_F_
U_
E_
L~~~4)1~
_,,,,.,.,____
s _u _s T
_ R_A_C_T_IN
-
0
4
:•• I
26
51
77
804'..4
· 80%
· 4-0%
255
•
•
•• COl.INTS •
,02 » 11s
138
154
179
205
230
· 20%
+ 1 O'o/o +.20'4
+4-0%
• 60%
+80%
· 10%
PERCENTAGE
•100%
I
Oo/o
I
NO ADJUSTMENT
5
02 and Fuel Trim Example
Fixed lean 02
•
1994 CHRYSLER CAR AA
IT
3.0L V6 MPI
A/C
51 sustained LEAN F/A CO
ITION
704 02S(V)_0.04 INJ(mS)_ 3.5
0 RPM
IGN CYCLES 1
3 IGN CYCLES 2
134
IGN CYCLES 3
0 OPEN/CLSD
LOOP CLSD
MAP SNSR(V)
1.2 MAN VAC("Hg)_ 19.2
BARO PRES("Hg)_28.9 THROTTLE( 0/o)
O
TPS(V)
0.82 MIN TPS(V) _ _0.82
2.3 COOLANT(l1F)
199
COOLANT(V)
ST ADAP( 0/o)
24.8 LT ADAP( 0/o)
24.8
EXHAUST
EAN VEH
0
SPEED(MPH)
Rich command (limit
reached as indicated by
both ST and LTFT o/o
being high .
•
•
•
This is a data capture of a vehicle
with a bad 02 sensor. (signal fixed
lean)
The computer's response to a lean
02 sensor is to add fuel. This process
of adding fuel will continue until the
02 sensor moves back to the rich
side of stoichiometric or until the fuel
trim has reached its limit.
This limit of control is different on
every car and is necessary to prevent
severe over or under fuelling
conditions.
This engine ran well cold and at WOT
and also during a forced open loop
condition.
- A forced open loop condition will
occur when an 02 sensor will not
respond to the computer's
command. A trouble code will
also be set at this time.
6
m'7 ~
~
Fuel Trim After Replacing 02 Sensor
This vehicle had a bad (fixed lea n) 02 sensor. The below picture is a scan data capture of what
the fuel trim numbers looked like with the new 02 sensor and the computer's memory not cleared .
Why is the LTFT commanding rich and the STFT commanding lean?
The computer is in the process of relearning. The memory (L TFT} was to add fuel from a bad
(fixed lean) 02 sensor. The new 02 is able to react and is telling the computer there is too much
fuel. The computer immediately responds using the STFT command to lean-out the mixture .
*I like to see this reaction, this tells me that the vehicle is fixed! My preference after a repair for a
lean condition is to watch the STFT and see how much it counters what the L TFT memory is
commanding. For an example, see the following video:
http://www.youtube .com/watch?v=Hmt LNJ9Gkl
Examples after a repair for a lean condition:
•
LTFT 30°/o STFT -25°/o = you fixed the problem (Total fuel trim is 5°/o, after the relearn
process the LTFT will be 5o/o and the ST FT will be 0°/o)
•
LTFT 30°/o STFT -10°/o = you still have a lean condition . (Total fuel trim is 20°/o, after the
relearn process the LTFT will be 20% and the STFT will be 0°/o) It's better but there is still a
problem .
0 2 Sens o r 112 Volts
0 . 67
L ong Term F T Bank 1
2 4 .2
Short Term FT Bank 1
-25.0
E ngin e R P M
782
7
For Low Power Complaints
The upstream 02 sensor must be functional (switching rich/lean) to use the
following test:
• At WOT every engine runs rich, so the 02 sensor should be reading over 800mv.
Just because the computer ignores the 02 sensor at WOT doesn't mean you have
to. You can use this as a guide to fuel delivery under load conditions.
• Test drive while watching 02 sensor millivolts at wide open throttle (WOT)
-
If the 02 drops lean (under 1OOmv) there is a fuel delivery problem. This is
most commonly caused by a dirty mass air flow (MAF) sensor or a low fuel
pressure/volume problem. http://www.youtube.com/watch?v=Hmt LNJ9Gkl
-
If the 02 stays rich (above 800 mv) then fuel delivery is good and you most
likely have a plugged exhaust causing the low power problem.
http://www.youtube.com/watch?v=9TlygJMxTps
8
Vacuum leak testing without a smoke nold'fine~
In general a Speed Densi ty engine (MAP only) will idle high (Figure 1) and a MAF engine will
idle low with a vacuum leak (Figure 2). This will change what the follo wing data parameters
(PIDs) look like.
http://www.youtube.com/watch?v=RFQBa-nqBPo
NOTE* Some vacuum leaks (especially manifold gasket areas) can on ly be located while the
engine is cold
•
External vacuum leaks
- Check for diagnostic trouble codes (DTCs). Look for lean exhaust and idle adaptive limit
codes . (Figure 3)
- Look at scan data
• 02 mv
• LTFT
• Idle A ir Control (IAC) motor position (see Section 20 for further /AC information)
• RPM and Desired Idle Speed
- Carefully spray propane around the intake and all vacuum hoses (FIRE HAZARD!!!!)
• Listen for RPM changes
• Watch 02 mv I STFT 0/o, (02 will go rich and STFT will go negative if you find the
leak)
- If you find a lea k and are having difficulty pinpointing the exact area
» Spray the sa me areas w ith water. You w ill be able to see and hear the
water getting sucked into the intake and no you won't hurt the engin e
w ith a small amount of water.
•
Internal vacuum leaks (V-type engines only) causing a single cylinder misfire
- Remove PCV valve and plug PCV port in the valve cover.
- Block off PCV breather port to the air cleaner. (Figure 3)
- Remove engine oil dipstick and install a vacuum gauge on the dipstick tube .
• There
should be NO vacuum in the crankcase. Crankcase pressure will actually
.
increase.
9
• If you read vacuum, there is an internal vacuum leak .
(Return)
MAP Engine With Vacuum LeaklOJJ"
Figure 1
\
-
''
'
.'
~
IAC Motor Position
.
'
''
.'
'
'
'
'
..I\
MAP Voltage
'
''
'
'
-
Engine RPM
v
r
/
2.49
IAC Counts Dropping
1
\
\
\
37
~
.:J 0
L_
\
steps 0
\
'
\'
1.67
v
' 1.67
1.2
1056
'
l
800
rpm
Fuel Control Status
Closed
Adapt Short Term
·1
%
Adapt Long Term
2
%
MAP Vacuum
17.6
Vacuum Leak Created Here
0.2
3.74
'
2.49
/
0.84
I
0.2\
'
'
Notice the increase in
RPM and P.W.
I
I
02Sensor1/1 Volts
lnj Base Pw Bank 1
•
I
8
•
800
iHg
Notice the 02 actually goes rich with this sudden
change in manifold pressure
10
(Return)
Figure 2
MAF Engine With Vacuum LeaklOJJ"
IVacuum leak created here
•••
0.72
02Voltage
I
8
I Computer Adding Fuel I
v
0.07
142
•
•
109
116
Integrator
109
106
107
Block Learn Mult
•'
•'
946
779
IAC Counts Increase
IdleAir Control
••
rpm
544
76
••
31
31
11
(Return)
Figure 3
Vacuum Leak cont.
Block off PCV and
breather hoses here
RPM
HC
A/f
4
z
D
AIR PASSES THROUGH
THE PCV INLET HOSE
TO THE VALVE COVER
AND CRANKCASE
VAPORS THEN PASS
THROUGH THE PCV
VALVE AND HOSE
····''
···-·PP•
co
02
coz ..
6
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,,
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6
I
1997 Intrepid 3.5 with a P0305 OTC. Lean misfire caused by
vacuum leak at #5 intake runner.
FRESH AIR MIXES
Wml BLOWBY GASES
IN THE CRANKCASE
Idle air A "O" count means
control this pintle is fully
~---.::~-~ actuato closed
'--~~~~~~~~
107
rrll 80
854
H02S B<rik 2Senso1l v
61B
Shat Te1mFT Bark 1
Short Te1m FT Bark 2
torg Teim FT Bart 1
O.B
Lorg Teim FT Bark 2
IAC Moto1Posiion
.: ngne Speed
Oe~red Ide Speed
rrll
93
O.B
I
0.0
9.4
0
cnt
902
1pm
640
rpm
Vacuum leak on bank 2, causing a 0 IAC count and an RPM that is
higher than desired idle speed. This car had no lean exhaust
DTCs but did have an idle adaptive limit code.
12
Misfire Diagnostics
Determine which cylinder and think about the cause (spark, air-fuel, compression)
1.
Scanner
•
Check DTCs and misfire counters (OBDll)
Some systems (Ford Trucks) may misidentify which cylinder is misfiring due to excessive timing
chain slack. Look at the firing order and check the cylinder before the identified misfire code.
Check freeze frame data
•
DTC .................... POlOl
Engine
SPD... 2567RPM
For a cold engine only misfire look for an intake manifold gasket leak.
ECT (
108°F
Digital Storage Oscilloscope (DSO)
VEmCLE SPD...54 MPH
ENGINE LOAD ..... 18.8°/o
•
Primary and secondary ignition (Figure 4, Figure 5 and Figure 6)
MAP............... 14.8 inHg
STAT l ...........OL
•
Relative compression (see examples on pages (Figures 7, §., ft., 10, 11, 12) FUEL
FUEL STAT 2 ....UNUSED
ST FT 1 ................. 3.1°/o
http://www.youtube.com/watch?v=SUSh072Grg8
LT F1' 1 ................-1.5°/g
Cylinder drop test (constant misfire only)
• Short out each cylinder one at a time and listen for RPM drops
http://www.youtube.com/watch?v=5ewJIBS9L98
• Can remove injector connectors, short out plug wires, or use scanner in a bi-directional mode on some
systems.
Gas analyzer
•
Tailpipe emissions http://www.youtube.com/watch?v=UzmoyoOOVpE
~~~~~~~~~~~~~~~~~~---+
0
2.
3.
4.
5.
6.
) ...............
A misfire from an injector not opening will have normal hydrocarbon (HC) readings.
A misfire from a compression or ignition problem will have high HC readings.
•
Check for HC's in the cooling system (head gasket problem)
There should never be the presence of unburned fuel (HC) in a cooling system.
Dipstick test (head gasket problems)
•
With a hot exhaust manifold, remove the oil dipstick and let it drip onto the manifold. If the oil bubbles
(like water dripped onto a hot stove) there is water in the oil. This is not a 100°/o accurate test. An early
head gasket failure may have no water in the oil.
Water test (intermittent secondary ignition problems)
•
Spray the entire secondary ignition system with water. Perform a snap-throttle test and see if it now
misfires. If it does you have a plug, wire, or coil problem.
13
(KerurnJ
Misfire Examples with 050 (snap throttle te~~
Figure 4
W 'r~~~~~~~~~~~~~~~~~
kU
No fuel misfire
15
3
. . . .
· · · ·. horted plu wire
. .
10
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s
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. . . . .
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Si na.l
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: 91 QI 4 . 3 181 13 OPER 'PtDC l'IIRE
Date:
1 na.. 2003 13: 33
I Deserlptlon
20 ~====~~==""'='"""'=='====~~~~~~~~~==:
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.
.
·-
Open plug wire
15
5
5
0
0
•
5
•
Pa.tf.e .. IV"Swee
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5Ms S
C
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.---!--:------:: problems
J. 1
I!'-----~~
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er
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a t. •1"1V"Swl e
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13
co ;(
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No fuel . nisfire
02 :.cC02 %
o.o
ZO-. l
0 .0
A/f R6t. io
0.0
I
--~
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-SB
:RPM Z Z OO
coz
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•. 4
No fuel misfire, injector
Aut.. ~
1.
co ;c
oz •
10
Tri er
Au.t..•
118
Two plug wires installed on wrong_ ___ _
.~ ---=
cy"'i-ders l snap thro e est
Mc ,.. ~ ...
15
Di" la
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Dia In.
Scale
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Sea.le
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S I na l
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.
s-
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fra..e C I
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14
(Return)
Figure 5
Misfire Example with DSO
. ... ... .. . . .. . . . .
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Carbon track
caused this shorted
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'
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15
(Return)
Primary Ignition Current Ramp
Figure 6
Turn On Oscillations
Turn Off Oscillations
Known Good
.,•
u
u
••
..
u
u
..
...,
u
...,
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-
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Open Plug Wire
.,•
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•
·16
CReturnJ Figure 7
•
Relative compression/ignition ti mi~ ~
~
Using a Scope (DSO) with a High Amp Probe
Fully charged battery, disable fuel, (can disable spark if you are not
performing a dual trace test), engine must not start or try to start.
Single Trace
• Connect
channel one using high amp probe to the starter BAT
•
wire
- Crank engine and watch for a uniform pattern with even peaks
and valleys
Dual Trace
• Connect
channel one using high amp probe to the starter BAT
•
wire
- Crank engine and watch for a uniform pattern with even peaks
and valleys
• For waste spark or conventional type ignition systems, connect
channel two using a capacitive type pick-up (also known as a
sync probe) to a secondary ignition wire.
• For coil over plug systems (COP) connect channel two to one of
the coil control wires (3 or 4 pin coils) or coil negative (2 pin coils)
- This will indicate 2 things
1. When the spark is occurring in relation to TDC
compression . See pages 20-22
2. Which cylinder has the compression problem (you must
know firing order) See pages 18-19
http://www.voutube.com/ watch ?v=WKdZsWU2Zml
http ://www.youtube.com/ wa tch ?v=spkpkRvQP HY
17
(Return) Figure 8
Relative Compression Testing
Jeep 4.0L Case Study
Single Trace Test
200
•;,:•==========J
~-·~··~·==~
~uk!n~
""ib~~u
~~··=
·
)=l
A
zoor==============================;
A
150
150
100
lCJO
50
so
Known Good
0
After Loosening One Spark Plug
0
-50 r,,.
o ----=n'--'.
~,-----..,:
n"""e----,.1.,°""'?_ __
1. Each picture shows starter current.
2. Amperage " humps" represent
compression in each cylinder.
200
A
,,,_
, ..~-• ...........i '
7
!=='=======-=-=··=· ==-=--=·===
-·===============;
150
100
3.
As the piston approaches TDC the
amperage output of the starter
increases from compression
building in the cylinder.
50
0
After Removing One Spark Plug
... ..
....
"
.
18
(Return)
Figure 9
••
Ford 4.0 Case Study
Dual Trace Test
A
#1
45 5
v
Secondary Sync Probe
Connected to #1 plug wire
1.0
0 .8
420
0.6
385
o..e
350
#5
0.2
315
#4
#2
#3
#6
0.0
280
-0.2
-0.'I
21
-0.8
Starter Current
10§.o
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
-1.0
2.0 s
Waste Spark Ignition System
Firing Order 1-4-2-5-3-6
Companion Cylinders 1/5-2/6-3/4
Cylinders 1 and 5 have the
compression problems.
19
(Return)
mV'
r:
Relative Compression vs. Ignition Timing
Figure 10
A
v
600
20
540
16
Secondary Sync Probe
Connected to coil wire
480
420
12
Notice the ignition firing event is taking place near TDC
360
240
·4
Starter Current
-8
'
-12
-16
60
0
-n.?
-11.1
n.n
n.1
n.?
n.~
0.4
n.s
n.fi
n.1
-20
n.a ~
4 cylinder with the correct ignition timing
20
Figure 11
(Return)
Relative Compression vs. Ignition Timing
v
A
1.0
Secondary Sync Probe
Connected to coil w ire
196
0.8
182
0.6
Notice the ignition firing event is taking place nowhere near
168
TDC
IS•
0.2
140
0.0
126
.2
11 2
-0.4
98
-0.6
-0.8
Starter Current
70
0.0
,_.
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
4 cylinder Subaru with the wrong timing marks used to line up
the new timing belt.
-1.0
2.0 s
21
(Return)
Figure 12
1996 Jeep 4.0 Case Study
E---
-
-
Camshaft Signal
Incorrect cam-crank relationship
Crankshaft Signal
Starter Current
, : . . - - - - (Relative Compression)
Coil Negative
~--- Voltage
Notice the spark (coil negative voltage spike) is not occurring anywhere nea r TDC as
indicated by the peaks of the starter current waveform . This was caused by an
incorrect cam-crank relationship due to a cracked/sh ifted flywheel. Short of
transmission removal and flywheel inspection there is simply no other test that would
verify this condition .
22
Multi-meter Basics
•
Testing Voltage
1.
The circuit must be loaded
(cu rrent flow)
•
No cu rrent flow =inaccu rate
readings (Figure 14)
2.
You must have a good ground for
the meter. W ith a bad ground all of
your test results will be wrong.
3.
Use battery ground for the
negative lead whenever possible.
4.
A voltmeter provides only average
read in gs . (Figure 13)
5.
A voltmeter reads difference in
potentia l between the two test
leads.
Testing Resistance
•
1.
Open circu it test
•
Start w ith lowest scale
One lead to each end of the
•
circuit
2.
Short to ground test
•
Start with highest scale
•
One lead must be connected
to a known good ground
l
2 v- - - - -
-.......-..
•
Testing Amperage
1.
2v
Voltmet e r
1 2 v-- - - - - -~....,
7v Voltmeter
5v ~----~__...___,
http://www.youtube. com/watch ?v=wO Pp LTnKKZg
2.
3.
Cu rrent can be measured
on positive or negative side
of a circu it.
An ammeter must be
connected in series .
Think of an ammeter as a
jumper wire with a gauge
on it. Wou ld you connect a
jumper wire from battery
positive to battery
negative?
23
Figure 13
Average Voltmeter Readings
(Return)
1lQ
I
!O
1100
I
10
llO
Ml
10 I
I
-40 1
I
·SO,.,...._--'
.so!
318.8
00
331 l
:ltl.8
368.8
•A DC Average Between rulers 2.584 V
•B DC Avera e Between rulers 628.6 mV
331.2
3SJ)
4CG.1
~138
The DC average readings you see to the left
is what a digital voltmeter would read on
these types of on/off signals.
24
mV'
r:
Voltage Drop Testing vs. Ohmmeter Testing
Figure 14
(Return)
1gn1con Swlldl
-
corroded
cable
Battery
With no current flow in the
main battery cable there Is
no voltage drop. tf the circuit
Is not loaded a voltmeter
reading will be inaccurate.
12v
-
oorroded
cable
Battery
Even though this main battery
cable is hot all the lime the
circuit needed to be loaded
(ignition switch In the crank
12v position) for the voltage drop
to be seen.
1v
oorrodec:t
cable
So why is the ohmmeter showing
no res istanoe? Because an
ohmmeter does not stress or toad
a circuit and there are sbll a few
good strands of copper wire in this
cable.
25
Battery testing
•
Ensure battery voltage is not dropping too low during cranking . This may
interfere with anti-theft systems and possibly cause a no start, no injector
pulse situation.
•
A battery that is shorted and will not take a charge must be replaced
before ANY further diagnostics can be performed. (see picture below)
'
''
'
'
12f........... . . ·'· . . . . . . ..
'
0
1O' ·
.,
8'· --- . . . , ...
'
'
6.
I
4~
'
''
''
'
•
•
••
•
''
'
''
'
'
''
.•
•
•
.
-- - -- - . - --
.•
I
0
•
•
.
- --·
y
••
-
-
,.,
•
, - - - --
I
I
--------------_,_ --------------.,,_ --------------
0
''
I
.
I
£ - - - - - - - - - - - - - - - . . - - - - - - - - - - - - - - .A. - - - - - - - - - - - - - -
- . "" - -- .. - -
- . -'
'
'.
'
''
''
'
'
- .... -- .. - "" -
.. - . - .. -· - ... -
''
''
'
-
''
''
'
'
''
''
'
''
'
'
''
- -- .. -- ~- - ---------- ~
''
''
'
.,'' .
'
''
'
''
•
••
•'
'
.,.
''
''
''
'
'
I
I
- - - ---- -1--------------' --- - ---- -- ~ - -- -- - --- _____ __________ 1___ - -- -- - -·- '
'
I
t
'
I
'
I
.
'
I
~ - - - - - - - - - - - - - - - .. - - - - - - - - - - - - - - _,_ - - - - - - - - - - - - - - .,,_ - - - - - - - - - - - - - - :
:'
The main problem here is there is too much AC voltage in this system for the engine
:'
'
'
2~---···· computer to function. The cause was a shorted battery. Engine would start with a jump ·····i
:
box, but not with the cha rger.
:
'
.
.
250
300
350
.
.
.
.
.
.
.
'
:
:
:
:
:
:
:
:
:ms
0'· .............................................................................................
J· ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
400
450
500
550
600
650
700
750
A = Battery Voltage with charge r on 250 amp start mode.
~-----------K
_O_
EC
_d_
u_
rin__no_s_
ta~
rt_
no_
s,j>ark. no inj._
ed
_o~
r e_ul_se_. D
_T_C_P0_3_20_ _ _ _ _ _ _ _ _ _~
26
Alternator testing
•
Current output
-
14
•
0
AC ripple test (diode test)
-
5s
2 .13U
Run eng ine at 2000 rpm with all
accessories on ( AC , blower on high ,
high beams , rear window defrost,
wipers on high )
• Watch scan data battery voltage
or check actual voltage at the
battery
• Make sure that system voltage is
over 13 volts ( ideal is 13.5 15.0 volts )
2.23Ul=IC
-
Run engine
. at 2000 rpm with all
accessories on
Connect voltmeter to alternator BAT
post and known good ground , set on
an AC scale
• Maximum allowable average AC
voltage is .3 volt (300mv)
Too much AC voltage allowed into
the system will cause major
driveability problems
27
Exhaust Backpressure Testing
•
Using a pressure gauge
Should be less than 2 psi at 3000 rpm (No loads, in park test)
• Most cars will read near 0 with a clear exhaust
0 psi during cranking
• Test locations
-
Upstream 02 sensor exhaust port
EGR backpressure transducer (Chrysler, Nissan)
EGR pressu re sensor (Ford)
If no gauge is available remove the 02 sensor and see if driveability
problem improves
http://www.youtube.com/watch?v=9TlygJMxTps "Testing for a plugged, clogged,
restricted exhaust, converter"
http://www.youtube .com/watch?v=Lafv2c4szZY "Exhaust Backpressure Testing"
28
Pre OBD II Catalytic converter funrtffi a naP1
testing
•
Using a gas analyzer
-
TEST 1 (running test)
•
Engine at normal operating
temp., remove and ground 1
plug wire
• Restart car and watch HC
-
HC should peak and then drop
1/3 of the peak if the converter is
good
TEST 2 (cranking test)
• Heat the converter
• Shut car off and disable the
ignition and c rank the engine
(injectors must be spraying)
• Watch C02 read ings == should
increase to a min . of 12°/o
•
Using an infra-red temp. gun
(running test)
-
Measure inlet and outlet
temperatures of the converter.
Catalytic converter tes~ pertormed on ahot cal duringcranking ~th ignit~n coil unplugged
C02%1ose over 13% withinafew seconds and was maintainer! lor at least 1n ~econds of cran~ng
Thi~ car also passes the HC test 'Mlilerunning (over ~ ppm peak,~n dropped IQ under 400)
• Outlet temp. should be at least
10°/o hotter than inlet
29
Switch lneuts
Section 2
Introduction
• Digital input to a
computer
• Signal voltage is
either high or low
(on/off)
• Opening and closing
of a switch causes
the signal voltage to
change
• There are two main
circuit designs
1. Pull-up
2. Pull-down
Examples of types of switch inputs
•
Mechanical/Hydraulic switches
Power steering pressure
Park/neutral
Transmission range and gear position
Throttle position
Headlight/parking light controls
Body computer inputs
•
Door lock/unlock
•
Cruise Control
•
Windshield wiper controls
• Door ajar
Climate controls
•
Electronic switches (no moving parts, a
transistor is the switch)
Hall effects, optical pick-ups
•
Crankshaft, camshaft, vehicle speed,
and newer design wheel speed
sensors
Communication between modules
•
Ignition module to PCM
•
PCM to Igniter
Frequency generating devices
•
GM MAF Sensors
•
Ford MAP Sensors
2
Pull down switch inputs
(Mechanical Type)
•
•
•
Signal voltage to the switch is
internally sourced by the computer
With the switch open, signal
voltage remains high
With the switch closed, signal
voltage gets pulled to ground
I
PCM
5 Volt
Regulator
1? v
• • • 5v
~
PCM
5Volt
Regulator
1
vvv
Voltage
Ov Sensing
Circuit
11
Voltage
5v Sensing
Circuit
,...----JL-----,
Think of this
as a voltmeter
3
Pull up switch inputs
(Mechanical Type)
PCM
•
•
•
Voltage to the switch is externally
sourced (does not come from the
computer)
With the switch open , signal
voltage is low
With the switch closed, signal
voltage is high
12~
-
pCM
A
v
11
Voltage
Ov Sensing
Circuit
11
___..._~Voltage
12v Sensing
Circuit
4
Switch Input ldentificatioW~ ~
~
(mechanical and hydraulic type)
1. Wiring diagram identification
-
Look at the switch and follow the wire that doesn't go to the
computer.
• If it goes to a ground then the circuit is pull-down.
• If it goes to power then the circuit is pull-up.
2. Voltmeter identification
- Check voltage levels on both sides of the switch.
- Force the switch to close
• Pull-down switch will show 0 volts on both wires with the switch
closed. (see figure 1)
• Pull-up switch will show high volts on both wires with the switch
closed. (see figure 8)
• Remember that the signal wire is always the wire that changes
voltage as the switch is opened and closed
- Both pull-up and pull-down, with the switch open or connector
unplugged , will read high volts on one side and 0 volts on the other.
To identify the circuit if you cannot close the switch you would need a
wiring diagram to know which of the two wires is the signal wire
(computer input wire).
» Switch unplugged, signal wire voltage is high = pull-down
» Switch unplugged, signal wire voltage is low = pull-up.
5
Honda Accord VTEC Oil Pressure S'10ldi
Circuit ID .
---
. .. ... ~-,.. L"'C ,,.. . . I:•si•• 'Prtf'o tw.a•c..-" ..,.• • D••r•• l ~<c-Onl .J:.>L
i
.--·=-
- -..
1 1 j
~
... ..,.,...
j -'
i
~
,, 0
r---r.
a•
•
"
J
•
I
•
..- •
Watch the video here:
http ://www.youtube.com/watch ?v=vTis29 MQC4 U
• •
I
•
6
Scan Tool Testing
(Mechanical or Hydraulic Type)
•
•
•
Check for OTCs (diagnostic trouble codes)
Find switch input data parameter (PIO)
Move the switch and watch for a change in state
- Scan tool will display either the voltage value, high/low or on/off
• If the data PIO changes state, the switch is working fine .
- If data PIO does not change , then voltmeter and switch input
bypass testing must be done to determine if there is a wiring or
switch problem.
7
Pull Down Testing
Mechanical or hydraulic type
•
•
•
•
•
Signal voltage measured
at the switch is fixed low (figure 3)
- Disconnect switch, if signal voltage goes
high = bad switch (figure 4)
- Perform a by-pass test to confirm
Signal voltage stays low with switch
disconnected
- Measure signal wire at the PCM (figure 5)
• Signal wire voltage is high at the PCM
and low at the switch = open wire
• Signal wire voltage low at the PCM
and low at the switch = short to
ground in the wire or a PCM
problem (figure 6)
Signal voltage low at the switch and PCM
- Check for a short to ground in the signal
wire with an ohmmeter, only an infinite
reading is acceptable
- No short = PCM problem (figure 7)
PCM not sending out voltage on the signal wire
- Check all PCM powers and grounds , and
refer to 5 volt ref. testing before replacing
the computer
Signal voltage measured at
the switch is fixed high (figure 2)
- Check switch ground , WITH THE
SWITCH CLOSED! (loaded circuit)
• Should be 1OOmv or less
- Check for mechanical or hydraulic
problems that would normally actuate the
switch
- If all the above checks are good, = bad
switch
- Perform a by-pass test to confirm
BYPASS TEST (figure 14)
-
Disconnect the switch and touch on and
off the signal wire , ha rness side w ith a test
light to ground . Signal voltage will get
pulled down . Look for some type of
response such as spa rk, inj ection pulse or
data PID change .
http://www.youtube.com/watch?v=yp kK6U8a64
http://www.youtube.com/watch?v=irHVjFTq4LE
"Chrysler Hall Effect Testing"
Note: figure 1 is what a good
working circuit looks like.
8
(Return)
Figure 1
Pull Down Switch Input
Normal Operation
PCM
Switch
' II
Signa.I Wire
•
tOv t
12v
PCM
Switch
S ignal Wire
tOv Ovt
9
(Return)
Signal Voltage Fixed High
Figure 2
(regardless of switch position)
Switch
•
...·· t
PCM
I I 1-I- - - · · - - - . ; . _ . . . - - - - - - - - - - - - ·
t
t
Ov
•
12v
Bad Swit ch
PCM
•
•.••· 1
I I ,..._ _.....,. - - - - - - - - - - - - - - - - - - - ·
t
t
1 2v closed 12v
Ov open
•
Open ground
10
(Return)
Figure 3
Signal Voltage Fixed Low
(regard less of switch position)
PCM
Switch
••
t··..
11--1----····· ......- - - - - - - - - ·
tOv
Possible Problems:
• Short to ground on the signal wire
• Shorted switch
• Open in the signal wire
• PCM problem
11
(Return)
Figure 4
PCM
Switch Disconnected
'•
t··...
,,,_ .......
----------·
l12v
.- Shot'~ ~e "9f"et.tfld- et=i-the-sigftel-wwe
• Shorted switch
r -Gperrin-the.al-'Mre
r 'PeMprobtern
12
(Return)
Figure 5
PCM
Switch Disconnected
i··
..
•11- ~ ...:..
I
12v
tOv
~~
~eigAO~w+re
r ~switetl
• Open in the signal wire
~ -PGM1)f8~1em
13
{Beturn)
Figure 6
PCM
Switch Disconnected
111- ·'- - - - - - - - - - Ov
Ov
/
• Short to ground on the signal wire
• PCM problem
14
(Return)
Figure 7
PCM
Switch and Computer Disconnected
• 1I
•""j\_
0 ohms
• Short to ground on the signal wire
le'""
• ..P€-M 1'f'ee
PCM
Switch and Computer Disconnected
11 I
•""-
I
j\_
• 1 +---4.--...J
infinity
- ~~-gretH'ld-efl~R&Si~~ wife ·
• PCM p roble m
15
Voltmeter Pull Up Testing
(Mech. Or Hydraulic Type)
•
•
Signal voltage measured at the
switch is fixed low (figure 9)
Check for mechanical or hydraulic
problems that would normally actuate
the switch
Check the external supply
voltage to the switch (with the
switch opened and closed) (figure
111
• Supply voltage should remain
constant regardless of switch
position, if supply voltage
changes with switch position
there is a short to ground in the
signal circuit.
Check the signal wire for short to
ground using an ohmmeter
No shorts and good supply = bad
switch (figure 10)
Note: Figure 8 is what a good
working circuit looks like
•
Signal volta~e measured at the switch is
fixed high (figure 12)
•
Check for mechanical or hydraulic problems that
would normally actuate the switch
- If all above tests good = bad switch
•
Signal voltage measured at the switch is
ood but is not recognized by the module
fi ure 13
•
•
Possible open in the signal w ire
Check signal wire at the computer
• Voltage stays at 0 regardless of switch
position = open in the signal wire
• Voltage gets pulled-up at the sensor and
at the computer= possible computer
problem
BYPASS TEST
(figure 14)
-
Disconnect the switch and touch on and off the
signal wire, harness side with a test light to
power. Signal voltage will get pulled up. Look
for some type of response such as spark,
injection pulse or data PID change.
http://www.youtube.com/watch?v=lzZNIPosGSY
(GM 24x crank sensor signal)
http://www.youtube.com/watch?v=OxP41MCd06w
(GM Camshaft sensor signal)
16
(Return)
Figure 8
Pull Up Switch Input Normal Operation
PCM
Switch
Signal Wire
(+)_.....-........_._ _ _
.:__ _--I
t t
12v
Ov
PCM
Switch
Signal Wire
(+)~........----.~------------1
l l
12v
12v
17
(Return)]
Figure 9
Signal Voltage Fixed Low
(regardless of switch position)
PCM
Switch
Signal Wire
__ .... --------,..,,~
Ov
• Bad Switch
• No Power Supply
• Short to Ground on Signal Wire
18
(Return)
Figure 10
PCM
Switch
•
Signal Wire
.
)
..
···t
_.....,.,
.....
,......
______
_
(+
12v
Ov
• Bad Switch
•-Ne-Pewer ~y
..-ShGR-te GFel::fRe-GA~.Wire
19
(Return)
Figure 11
Switc h
•
(+)
.
··t
•· ...
••
tOv
Signal Wire
tOv
.. ~ae~~
• No Power Supply
-.SR9~ k>-bf"~en S~WiFe
••
•••• f
PCM
Signal Wl re
(+)---·····---------I
t
t
12v open
Ov
During a bypass test the
test light will light
confirming a short to
0 closed
ground on the signal
- ~ae~wilE*l
wire
.. ~~ewer-Swppl y
• Sho rt to Ground on Signal Wire
(This is more of a concern on electronic type switch input circuits)
20
(Return)
Figure 12
Signal Voltage Fixed High
(regardless of switch position)
PCM
(+)
Switch
•
...··1
-- ..... -------- --·
l
12v
• Bad Switch
21
(Return)
Figure 13
Signal voltage changes with switch but not
recognized by the PCM
PCM
Switch
••··}
Signal Wire
(+)-----4·····......------~·
t
Ov open
12v closed
I
Ov constant
• open signal wire
Switch
•
..·· i
PCM
Signal W ire
(+) --·······- -----------·
t
Ov open
12v closed
I
Ov open
12v closed
• PCM problem or PCM connector problem
22
(Return)pg. 8
(Return)pg. 16
Figure 14
Switch Input Bypass Testing
PCM
Switch
• llj--
. .
....
Signal Wire
--~~~~~~~~~~
Pull-Down
Design
To uch the test light onl off to the signal
wire and look for a response.
PCM
Switch
(+)-
. .
....
Signal Wire
--~~~~~~~~~.......
Pull-Up
Design
12v
23
How to Identify an Electronic Type SwitcITT"n~ut
Circuit Design
•
It must be done with a voltmeter or scope.
•
•
A wiring diagram will usually not show circuit design.
On hall effects and optical pick-ups, disconnect the sensor and measure signal
voltage on the harness side. KOEO or KOER
•
- Signal voltage is high = pull-down design
- Signal voltage is low= pull-up design
On module to module communication circuits, disconnecting one of the modules
will not identify circuit design in all cases. Leave the modules plugged in and
measure signal voltage with the KOEO or KOER (if it runs).
-
•
If signal voltage is high you can pull the circuit down with a test light
connected to ground.
If signal voltage is low you can pull the circuit up with a test light connected to
battery positive.
• This test will be used primarily on PCM to Igniter/Ignition Module control
circuits when there is a no spark or no injection pulse condition and there
is no signal on this circuit. http://www.youtube.com/watch?v=VG3EZJlyjl8
An open or shorted signal wire will cause misdiagnosis of circuit design.
- The only way to be 100°/o sure is to test known good circuits and document
24
your findings for future reference.
m " " "'
Frequency Generating Device GM 3-Wire MAF
r7
V
..
•
Sensor
Unplugged
0
0
.. ~ii::
•
•
•
I
I
4 .99U
14
L
..
L
.
I
•
j
I
I
I
I
I
I
I
I
I
I
I
I
I
I
•
•I
!
0
I
5 .06UDC
I
Engine running , sensor
plugged in , there
shou ld be a sq uare
wave pattern here
~
1
I
I
I
I
,_ ~ii::
I
I
0.76U
I
I
I
I
I
14
•
L
L
L
L
0
••
0 .83UDC
The above picture is the signal voltage of a 3 - wire GM MAF sensor. Measured at the sensor,
backprobing , with the sensor unplugged and plugged in.
The key to proper diagnosis is to know what the signal circuit design is and what a proper
signal should look like. On this type of MAF the ECM sends 5v down the signal wire to the MAF
sensor, and the MAF "pu ll s it to ground" to create a varying frequency based on air flow.
This is a pull-down design circuit.
1. With sensor unplugged the signal wire voltage should be 5 volts. This tells you that the
ECM is good and the signal wire is not opened or shorted. No need to use the ohmmeter
here! You have a bad MAF sensor.
2. If the signal voltage remained low with the sensor unplugged then you would need to look
toward the ECM or signal wire and not the MAF sensor.
25
Electronic Pull-down desi
GM 3300 Dual Crank Sensor
v
8
6
-•
...
~
. . I . . I . ..' 1 .
. .
. Cold Engine
. .. . .
. . . . .. . .
l . . . . .. .
. .
.
.
,.. .
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v
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50
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150
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.
6 ,.. . . . . . . . . . . . . . . .. . . . . . . . . ....
.
4 ,.. . . . . . This Jest confirms that the . . ..
2 r· . .
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_.,
Hot Engine
.
.
. ... . .
...
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Final Test, Sensor
Unplugged
..
-2 0
v
..
-,.. . No. .Start,. .No Spark
. .
.
2 ,.. . .
0
300
:
-z 0
8
200
.
.
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v " ,.. . . . . .
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·module· and w·iring. are good
..
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.
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.
.
.
.
..
bad.. ·sensor
.
-
;
;
This is an example of en electronic
switch input. This is a 7 volt pull -down
design hall effect. (The module supplies
7 volts to the sensor and the sensor
pulls it to ground to generate the square
wave signal.) In all of the captures the
scope was connected to the crank
sensor signal wires at the module .
'
Why is the signal voltage so low in this bottom capture? Is the sensor bad? Is there a
wiring problem? Or is the module not sending out the proper voltage? The key is to
understand signal circuit design and what the "final test, sensor unplugged" capture
tells v ou
26
~
Module to Module Communica ion
<=1
FORD TFI IGNITION EXAMPLE
PIP Signal \Vire
PCM
0
G
CKP+
ICM
CKP·
CKP
ICM to PCM communication wire, known as the PIP (profile ignition pickup) wire is a
square wave signal generated by the ICM and sent to the PCM. This is a pull-up
design circuit where the module supplies the 0 to 12 volt square wave to the PCM
based on the input from the CKP signal. If you know circuit design you can quickly
and accurately identify whether there is a wiring , module or crank sensor problem.
The following test would be performed on a system that had no signal on the Pl P wire
and no injection pulse from the PCM.
Perform a bypass test:
1. KOEO
2.
Connect a test light to battery(+) and touch on and off the PIP wire.
3.
PCM should respond by firing injectors
•
If it does then the PIP wire is not opened or shorted and the PCM is
good, and our focus is now on the ICM or CKP for the problem.
27
Module to Module Communica ion
<=1
~
GM HEI IGNITION EXAMPLE
ICM to PCM communication wire, known as the Reference wire is a square wave
signal generated by the ICM and sent to the PCM. This is a pull-up design circuitt.
Where the module supplies the 0 to 5 volt square wave to the PCM based on the
input from the CKP signal. If you know circuit design you can quickly and accurately
identify whether there is a wiring, module or crank sensor problem. The following
test would be performed on a system that had no signal on the reference wire and
no injection pulse from the PCM .
Reference Wire
0
CKP
ICM
PCM
EST Wire
G
Coil
Perform a bypass test:
1. KOEO
2.
Connect a test light to battery (+) and touch on and off the Reference wire.
3.
PCM should respond by firing injectors
•
If it does then the Reference wire is not opened or shorted and the PCM is
good, and our focus is now on the ICM or CKP for the problem.
28
Circuit Designs
•
•
•
•
•
0
G
•
•
•
•
•
90 Cadillac Seville 4.5 CMP Sensor
Pull-up (CMP pulls up 12v signal to PCM)
GM DI and early El systems, the ICM to PCM REF . circuit (purple-white) is a 5 volt pull-up design.
The ICM sends a 0 to 5 volt square wave to the PCM.
GM 3800 CMP ckt.
CMP to ICM
• Pull-down (ICM sends CMP 7v, CMP pulls it down)
ICM to PCM, CMP signal
• Pull-up (ICM sends 5v pull-up signal to PCM for camshaft reference)
95 Ford Windstar 3.8 waste spark ignition. PIP Signal
Pull-up (12v), gry/org wire to pin 49 of PCM. ICM rece ives AC signal from VRS ckp. ICM coverts to digital PIP
signal and sends to PCM.
94 Ford Probe DI ignition with remote mounted ICM, 4 wire dist. Connector.
Dual Hall Effect in distri butor. 1 = PIP Signal, 2 = CID Signal
PIP Signal = red/yel wire is a 12v pull down circuit supplied by PCM pin 56.
CID Signal = pull-down (12v)
GM 3-wire MAF
Signal circuit is a 5 volt pull-down (PCM sends 5 volts to MAF, MAF pulls it to ground)
GM 3300 CKP
Pull- down (ICM sends 7 volts to CKP, CKP pulls the signal down)
92 Chevy Caprice 5.0 ESC Module
Pull-up design (ESC sends 1Ov to PCM, when there is no knock, during knock 0 volts is sent to the PCM)
Dodge Caravan Fan Module
Fan Module sends 12v to PCM all the time (even key off), PCM pulls the circuit down to turn on the fan. (PCM
pulses the circuit for low speed and fully grounds it for high speed)
2004 Nissan Altima 2.5 (VIN A) CMP Sensor (pull-up design). 12v feed , g round , signal. The signal is a 0/12 vo lt
square wave. There is no voltage on the signal wire with the sensor unplugged . Engine will run without CKP input
due to CMP design.
29
Circuit Designs
•
•
•
•
•
•
0
G
•
1992 Honda Prelude VSS Hall Effect
5v pull-down signal
2002 Gallant 2 .4 Cooling fan controller. T he PCM turns the fans off by applying a ground to the control wire
between PCM and controller. No ground = both fans on
1992 Buick Lesabre 3800 CMP Sensor
Pull-down design
• ICM sends 12v to the CMP, CMP pulls it to ground
1997 Monte Carlo 3100 VIN M CMP Sensor
Pull-up Design
• CMP Sensor sends a 10 to 11 volt signal to PCM
1989 Honda Civic 1 .5 Igniter Signal
Igniter sends 10 volts to PCM, PCM pulls the circuit to ground to control Igniter transistor.
Ford Digital MAP Sensor
Pull-up design
• The map sensor sends a 0 to 5 volt square wave to the PCM
1993 Nissan Sentra/Maxima PCM to Igniter Control Signal
Pull-up design
• With connector unplugged and cranking PCM sends 12v on/off pulse to the igniter
• With connector plugged in and cranking this same pulse drops to around 4 volts
Add to this list on your own as you learn more system designs, which will make you
faster and more accurate in the field.
30
0
G
Transistor Drivers and
Outeut Solenoids
Section 3
Warning
Please read this carefully! If you do not follow exactly what is taught in this section you
can and will damage sensitive electronic circuits inside of the computer. I am explicitly
drawing your attention to these procedures, which - done properly - allow you to
quickly and accurately identify solenoid operation WITHOUT removing the solenoid
from its location. This is vital for a number of reasons outlined below:
•
To identify a sticking solenoid you never want to remove it from its normal location.
The vibrations created by removing the solenoid to test it will cause the solenoid to
unstick, making an accurate diagnosis impossible.
•
While following a 3 page flow chart, you are told to remove the solenoid to test it.
The solenoid is not easily accessible and would take an hour to remove it. This
hour spent removing the solenoid may be a complete waste of time! The solenoid
could end up being good! It is more effective to test the solenoid where it "lives",
without removing it!
0
G
•
•
There are no scan tool bi-directional controls.
Bi-directional controls for solenoids are limited to KOEO only. What if you need the
solenoid to function with the engine running? Such as when testing for EGR flow
problems.
With these procedures I am teaching you how to "be the computer'', that is, turn on the
solenoid as the computer would do.
The testing methods used in this section are universal concepts and apply across the
board into any and all types of switched circuitry including non-automotive related
circuits.
2
Introduction
•
•
There are two basic ways a computer will energize an output solenoid. (see figure 1)
1. By controlling its power supply
2. By controlling its ground
To determine if the solenoid is power or ground side controlled.
1. Use a wiring diagram
• Remember that a solenoid needs a power and a ground to work. Follow
both wires. The wire that goes to the computer is the "control wire". The wire
that doesn't go to the computer will ALWAYS tell you what's in the
computer. (see figure 1)
http://www.youtube.com /watch?v=pH kjRwD-Xw (start watching at the 4: 11)
0
2. Use a voltmeter, KOEO (key on, engine off) check voltage on both solenoid
wires. With the solenoid NOT energized. (see figure 2)
• +12v on both wires =this is a ground side switched solenoid
• Ov on both wires = this is a power side switched solenoid
» NOTE - with the solenoid energized both types will read + 12v on
one wire and near Ov on the other
G
http://www.youtube.com /watch?v=pkcwNkkNWYA
•
To be able to quickly identify a problem with an output you must
- know how the solenoid is controlled (see figure 3~
- Determine if the solenoid normally open or normally closed (see figure 4 )
- Know how to energize and de-energize the solenoid both manually and with
scanner bi-d irectional controls.
3
[Return Figure 1
Power Side Switched Circuit
PCM
Solenoid
11 ......- - -
Shows circuit design
Control Wire
PCM
0
G
Fuse
Transistor
"Driver"
Solenoid
12v_
Ground Side Switched Circuit
A transistor is nothing more than an electron ic switch. These circu its are controlled by switching
on/off the power supply or the ground to the solenoids. Wiring diagrams do not provide an inside
view of the PCM (as I have) so circuit identification is achieved by following the wire that does not go
to the PCM.
4
Return
Figure 2
0
Power Side
Switched
0
O ff
control
On
12
0
G
• You cannot determine circuit design with the solenoid on because both designs look the
same. To identify the circuit design with a voltmeter the solenoid must be off.
• To determine which of the two solenoid wires is the control wire (see figure 3)
12
12
O ff
Ground Side
Switched
control
On
12
0
5
Return
Figure 3
Circuit Identification Using a VoltmetePJl'V ~
(known good circuits)
Power Side Switched
Ground Side Switched
SolGnoid
SolGnold
Ov - Solenoid
0
G
12v- -
12 v
Test Light
off
Solenoid
Test Light
on/
.......,\
,,.......
12v
·--~ov
Control W ire
Constant Ground
Ov- •
Control Wire
- - 12v
Constant Power
Notice is these pictures that solenoid circuit identification (power/ground switching)
is done by measuring voltage levels on both sides of the solenoid. Also control
wire identification can be done by unplugging the solenoid. This method can be
used on any ground or power side switched ci rcuit, not just solenoids.
6
Return
Figure 4
Normally Open Solenoid
i--~-
Normally Closed Solenoid
Ov
Off
Off
On
On
0
0
It is important to understand the mechanical differences between solenoids when
testing them for normal operation. With the solenoids energized, a normally closed
type wi ll have flow and a normally open type will block flow.
7
http://www.youtube.com/watch'~riizJ 1dg ~A1
http://www.youtube.com/watch?v=QYtYSgglJoY
http://www.youtube.com/watch?v=pH kjRwD-Xw
Solenoid Functional Test
0
G
To safely energize the solenoid
use a test light connected with the
correct polarity and touch on the
control wire with the KOEO or
KOER (be the computer). Listen
for a click and a change of state in
the solenoid. This test will only
work on low current solenoids.
If you accidently connect the test
light to the wrong polarity you will
not harm the computer transistor.
The brightness of the test light bulb
will depend on the resistance of
the bulb and the component you
are testing.
With low ohm
solenoids the test light will be
bright. With high ohm solenoids
the test light will be dim.
For higher current solenoids a
jumper wire is necessary. Perform
the same test as illustrated in the
pictures using a jumper wire
instead of a test light.
If you accidently connect the
jumper wire to the wrong polarity
you WI LL "fry" the computer
transistor!
PCM
fuse
12
Solenoid
v_.. ---
................!
:: 'i
:
t
,{ Test Lighl
Transistor Oil
PCM
Solenoid
llt----.-...-...--..........,
·•
:'
/
! i \ Test Ught
•
:
'
Transistor Oil
12v
8
Test Light Current vs. Solenoid Cu~rff
•
Test light current examples:
-
•
Thexton (I use this one to energize
solenoids)
• .43A @ 12.SVDC
• .47A@ 14.SVDC
-
Mac (I use this
computer drivers)
one
to
~
Solenoid current
-
Solenoids tested ranged from .3A to
.SA (low current) and . 7A to 1.0A
(high current)@ 14.SVDC
-
Relay coil current is around .1A
check
• .1 4A@ 12.SVDC
• .17A@ 14.SVDC
•
Determine test light current draw by connecting it in series with an ammeter.
0
•
A test light that only draws .1 to .2 of an amp will not energize most solenoids, but will have no
problem energ izing relay coils.
G
•
A test light that draws more than .3 of an amp will energize most solenoids. Even if it is only
partially energized there is usually enough magnetic field strength to ma ke the solenoid iron
core move .
•
Use a jumper wire for solenoids that need .5 of an amp or more. WARNING: A JUMPER
WIRE CONNECTED TO THE WRONG POLARITY MAY OVERLOAD THE COMPUTER
DRIVER AND "FRY" IT!!!
•
When checking transistor drivers, it is safer to use a test light that draws very little current
especially on relay coil drivers. You could potentially overload and "fry" a computer driver even
w ith your test light. Just make sure your test light current draw is less than .3 of an amp or
300ma .
9
A Warning on Using Jumper Wires on Output Circuits
••• ••••
••• •••
PCM
••• •••
• • • •••
Solenoid
•••
-.. • • • •.
~.~ • •
•••
11.-----..f'"'V""l"'~----~1-·-··-·....· ·...·..,··r-·~·!-:.1~· ..... ·12~
• • • •• •...
:.................
•
••••
••
••
j umper wire
:
••••• • • • •
• •:" • •
.... - '
...
...
•• •••
•••
•••
0
•
•••
•• ~e
• • • ••
Transis tor On
... •••
• ••
• ••
• •• •
•••
• ••• • ••
••••
PC M
Solenoid
:••••••••••••••••
•
•
• ••• ••• •.Jumper wire
• • • • •.
•••
-
11
:
. ......
:
•
Trans1&lor On
••\
12v
••• • •••
A jumper wire connected like th is will not energize the solenoid . The only th ing that would happen
is you w ill "fry" the driver if it happened to be "on". NEVER CON NECT A JUMPER WIRE LIKE
THIS!
PCM
PC M
G
Solenoid
Fuse
12V--J
11 - -....................
- -...
•
•
•
•
•
••
••
•
•
................,• '9-----+-~"""'""-1 1 1
••
j umper w ire
ju mper wire
•
•
Transistor Oil
12v
Solenoid
••
••
t
Transtslor Oil
-
A jumper wire connected like th is will energize the solenoid. Even if the driver happened to be
on you would not hurt the driver due to equal potential. Pay attention to circuit design and
jumper wire polarity. If in doubt do not perfo rm this test! Remove the solenoid and run your
own power and ground to test the solenoid instead.
10
mV'~
@
A Warning on Using T-pins on Outputs Circuits
PCM
Solenoid
Solenoid
Fuse
\o------+-i.t"')r- 12v
!It-----
PCM
12v__,
T-pln
0
0
T-pin
If this T-pin touches body
ground you will "fry" the PCM
driver if it happens to be "on".
Be extra cautious on power side
switched circuits.
••• •••
Trans slor On
If this T-pin touches body
ground you w ill not damage
anything. You will just energ ize
the solenoid.
Trans slor On
PCM
••••••••
••• •••
•• • • • • • •
'd
Soleno1
• •. • • • •
•••
Fuse
~ •••• ••
• •• • ••
•••••
• &tflfo1d
•
••
• ••
t-----+-__,,~·11""·· · 12v...
...•• 3lv
·
... · · · · · ·r---<
T-p1n
I-~ ••• •••
T-pin
•••
••• •••
•••
••• •••
•••
• •• • . .
Trans sl0t On
• •• • ••
····l iW\.
. ••
• •
T-pin
• •• • ••
••• •••
• •••
Trans.slor On
• •• • ••
•••
••
•••• •••
Never use two T-pins on a solenoid connector. On either circuit design if the T-pins touch
each other and the driver happens to be "on" you will "fry" the PCM driver.
11
ro'
7
~
Testing Computer Drivers and Control Circuit
~
Integrity
http://www.youtube.com/watch?v=MOSH8XLKrlc
http://www.youtube.com/watch?v=8FnYllf5D9E
Ground Side Switched Circuit Test
Power Side Switched Circuit Test
PCM
PCM
unplugged
Solenoid
Solenoid
~ rYYY'\
Fuse
12v----'\r--
••
•••
•
' ,- :
/
Tes1 Lighl /
on
0
G
-................ ..
••
1
'f
I
11
Translslor On
•
12v
11---Test Light -
on
/
-
PCM
Solen old
Fuse
' ...'/
,• ..................
/
12v
•
••
•
•
•
••
••
~
Transistor On
T
PCM
Solenoid
rYYY'\
12V----'\r--
'
Test llgl\t
F
: 1t
11-1- -
'
off
Tra nsls1or Off
12v
12 v
""-
~
Tesl Llghl
off
f
~
...-
Transistor Off
Force the transistor to turn on and off by using a scanner in bi-directional mode or by meeting the
running conditions that the transistor needs to turn on. This test is usually performed when there
is a shorted or open solenoid and there is concern that the transistor may have been damaged.
The above pictures show what the test light will look like with a good driver and control wire .
12
Ground Side Switched Circuit Problems
(see page 14 for what normal circuit voltage levels should look like)
High volts (12v) on the control wire with the driver commanded
"on" (backprobing the solenoid connector) (see figure 6a)
-
0
G
Check control wire voltage at the PCM
• Reads 12+ volts= PCM driver problems (see figure 6b)
- Must check all inputs that affect this driver before condemning the
PCM
- Check PCM connector for pin contact problems
- Must check all PCM powers and grounds before condemning the
PCM
- Remember that the PCM will at times shut off an output solenoid if it
doesn't like the current flow from the solenoid circuit or if the voltage
level is incorrect for the solenoid command ("on" should be low
voltage and "off' should be high voltage)
• Reads 0 volts = open in the control wire (see figure 6c)
13
(Return) Figure 5
Ground Side Switched Circuit Normal
Operation
PC M
l osM
Solenoid
Fuse
12v_..
(Output state monitor1 measures control wire
voltage and current
flow)
Trans istor Off
0
Normal Operation
G
Fuse
12v_..
PC M
l osM
Solenoid
t
~t----+--6---.e- ........... ,.
12v
Ov
Transis tor On
14
Return
Figure 6
PCM
Fuse
a.
Possible causes: --~ 12v__,
• Open control wire
• Open driver
Solenoid
'-t_ _____,.____,,~--111
t
12v
12v
Transistor On
PCM
0
Solenoid
Fuse
b.
•
Open driver
--~ 12v__,
CD
'-----"'--..e--...-~11
l
12v
l
12v
~
12v
Transislor On
PCM
Fuse
c.
•
Open control wire
Solenoid
--) 12v.-
t
12v
TranS1stor On
15
Ground Side Switched Circuit ProbfelJmi
~
Low volts (Ov) on the control wire with the driver commanded "off"
0
G
(backprobing the solenoid connector) ((see figure la),
1.
Use a test Light http://www.youtube.com /watch?v =Wt zT JWbDzs
Connect test light to battery (+) and touch on the control wire (solenoid
unplugged)
1.
Test light on = shorted control or shorted driver {see figure lb)]
Key off, unplug PCM connector (s)
•
Test light still lit= shorted control wire (see figure le)
Test light goes out= shorted PCM driver (see figure ld)
2.
Test light off= open solenoid or solenoid connector (see figure le)
Check solenoid and connector with an ohmmeter
2.
Use an amp probe
Connect amp probe to the feed or control
1.
Constant current flow = shorted control or shorted driver (see figure Ba)
•
Key off, unplug PCM connector(s)
Key on, recheck current flow
•
No flow = shorted driver (Make sure you still have feed voltage
available to the solenoid after unplugging PCM. The PCM may be
controlling a relay that powers up that circuit. If you unplug the PCM
the relay will shut off and you will lose the 12v feed to the solenoid
causing misdiagnosis!) (see figure Bel
Flow = shorted control wire (see figure Bd)
2.
No current flow = open solenoid or solenoid connector (see figure Bb)
Check solenoid and connector with an ohmmeter
•
16
Return
Figure 7
PCM
a.
Solenoid (disconnected}
Fulie
Solenoid
Fu&e
PCM
d.
Unplugged '
12v --'\.r---
12v__.
1--~~1 1
Test Light
off
Ope n solenoid
S horted control wire
S horted Driver
Trans1slor Olf
PCM
b.
Solenoid (disconnected)
G
12v
PCM
e.
Fu&e
0
• - -Gpe•1<1oleneid
• - - Slol()f(EMI iM>IWelo wire
Shorted Driver
Transistor Off
Solenoid (disconnected}
Fulie
12v--'\,r---
,......---+---,c~-11 1
Test Light
Transistor Olf
• -
-0~A-sei9"oid
•
S horted control wire
Shorted Driver
Open solenoid
olf
- - .$herle~og~l.wi'8
• - -Slol()f(e<i Bri...er
12v
Transistor Off
12v
PCM
c.
Solenoid (disconnected}
Fuse
rYYY\
Unplugged .........
2v--'\.r---
I
"I
'/
-
Test Light -
· - .ope.. sel9'laid on
/
'
I
,11
-•
Transistor Off
Shorted control wire
· - - Sh"'1ed e riYer
12v
17
Return Figure 8
a.
PCM
Solenoid
Fuse
l
12v
PCM
b.
Solenoid
Fuse
.l.
+---~i----rr........tll
l
Qy
12v
A (curent !low)
Transistor Orr
A (no CUITlll11 now)
Inductive
Ammeter
0
G
Inductive
Ammeter
Circuit is shorted to ground
Open coil winding or connector
PCM
c.
PCM
d.
unpligged
Solenoid
Fuse
\
12v12v
'
Qy
12v
A
Make sure you still
have 12v here
during this test
(no CUITlll11 now)
Inductive
Ammeter
Shorted driver
Transistor Orr
Transistor OH
11
l
Ov
A (curent flow)
Transistor OH
Inductive
Ammeter
Short to ground on control wire
18
Feed Circuit Problems
PCM
Corroded Feed Wire
Fuse
Solenoid
12v ~ ----
.
t
1 2v
0
0
t
~onnal circuit
off" read ings
1 2v
'--------1--....--...~ 11
f
1 2v
Trans1Sto r Off
Unwanted voltage drop on the feed side of the solenoid
which is only visible with the ci rcuit loaded (current
flowing).
Fuse
PCM
Solenoid
Tran sisto r On
To properly test voltage on ANY circuit there must be current flow. "The circuit
must be loaded"
19
Power Side Switched Circuit Probl~f
~
(see page 21 for what normal circuit voltage levels should look like)
•
Low volts (Ov) on the control wire with the driver commanded "on" (backprobing
th e so le noid connector)
-
0
G
•
Possible problems: (figure 9a)
• Open in the control wire
• Faulty PCM driver
• PCM is intentionally not turning on the solenoid ("driver shut-down") due to
incorrect voltage or current levels. This is usually caused by an open or
shorted solenoid and will also set a trouble code. As long as there is a
current code for the solenoid in memory, the driver for that solenoid WILL
NOT turn on.
Measure control wire voltage at the PCM
- 12v = there is an open in the control wire between the PCM and the solenoid
(figure 9b)
-
Ov = the PCM is not turning on the driver or the driver is bad (figure 9c~
• Check the resistance of the solenoid coil. If it is open or shorted the PCM
may not turn the driver on. Disconnect the solenoid and touch on the
control wire with a test light connected to ground. Clear trouble codes and
command the driver on (test light must be connected before clearing
codes). If the test light lights the driver is good and an open or shorted
solenoid was causing the PCM to shut down the circuit. (figure 9d)
20
(Return)
Power Side Switched Circuit Normal Operation
PC M
losM
Solenoid
I
I
12v
Normal Operation
G
l
Ov
Transistor On
PC M
losM
Solenoid
•I
12v
l
l
Dv
0
(Output state monitormeasures control wire
voltage and current
flow)
12v
l
Dv
Transistor Off
21
(Return) Figure 9
PCM
a.
PCM
c.
Solenoid
Solenoid
llti----
l
l
Qy
•
•
•
0
G
II
I
-J J
.
l
l
Qy
Ov
-
I ..-...
,j
Ov
Ov
Transistor On
Transistor On
Open control wire
Open driver
Driver "shut down" from a faulty solenoid
•
•
•
,. 12v
Opec = tr.ol.wira.
Open driver
Driver "shut down" from a faulty solenoid
PCM
PCM
Solenoid
b.
Solenoid
,.,,,,
--
11
l
Ov
•
•
•
l
Ov
-
I
..-
12v
,
12v
1 11~--
I
••
•
•
...- '
•
Of*l!'l eoRtFOl-wir&-
•
•
0~ drio.<er
.. - ' '
••
' '- :
Test Light •
on
/
,j
Transistor On
Open control wire
Gpe"°dt'ivel'0rio.<et ''slttll-dewn'- "'°"1-9 .fettll'; sofel'IOid
, ..... ...........
•
12v
~
Transistor On
Driver "shut down" from a faulty solenoid
22
Power Side Switched Circuit Problems (continued)
•
Normal voltage readings on both the control wire and the ground wire to the
solenoid, 1(figure 1Oa, 1Ob) however the solenoid is not functional and/or there is a
trouble code set in memory.
-
0
G
-
Connect an amp probe to the control wire and measure current flow with the
circuit "on". If there is no current flow with a good power and ground, this
indicates an open coil winding in the solenoid. (figure 1Oc)
For additional confirmation you can disconnect the solenoid and measure
resistance of the solenoid winding.
• Note - An ohmmeter test of a coil may not be 100°/o accurate, in particular
on higher amperage solenoids. A solenoid can measure the correct
resistance with an ohmmeter but when normal power and ground is sent to
the coil the winding opens up due to heat. This is why an amp
measurement may be necessary.
23
(Return) Figure 10
a.
b.
PCM
PCM
Solenoid
Solenoid
11~---
0
'-----+----illl"">r-12v
' '
Qy
12Y
11
I
--
l
f '
Qy
Transistor On
Normal circuit "on" readings
l
Ov
., I
12v
-'
~
TranS1stor Off
Normal circuit "off' readings
G
PCM
c.
__
,,...._
Solenoid
_,
l
Ov
. ........
''
l
12v
.., I
(no current flow)
~-
-
12v
...
Transistor On
A
Abnormal current
reading
Inductive
Ammeter
24
Power Side Switched Circuit Problems
•
High volts on the control wire with the driver commanded "off" (backprobing
the solenoid connector)
- Possible problems:
• Shorted driver allowing current flow all the time
• Control wire shorted to battery positive
• Normal condition with an open solenoid winding or bad solenoid ground.
This will cause bias line voltage to read near battery volts. (Not all systems
use this bias, you just need to be aware of it and not let it fool you) (figure
0
G
l111l
•
Connect a test light to battery negative and touch on the control wire (solenoid
unplugged)
-Test light lights = shorted driver or control wire
•Disconnect the PCM
- test light goes out= shorted driver
- test light still lit = shorted control wire
- Test light does not light = the voltage you where seeing in the original test was a
bias voltage that is now being pulled to ground through the test light.
25
(Return)
ffi'V ~
Figure 11
~
Power Side Switched Circuit Bias Voltage
0
G
•
There is a variable when it comes to power side switched solenoids. Some systems run a bias
voltage on the control w ire for the solenoid. Th is is a very weak voltage signal that is easily pulled
to ground through the windings of the solenoid. With the solenoid "off' and plugged in (good
solenoid) the solenoid itself will pull down th is bias voltage to near zero volts (left picture). If you
unplug the solenoid you w ill see a voltage of near battery volts (right pictu re).
•
This can be confusing because an open in the solenoid winding w ill cause high voltage to be seen
on the control wire . This high voltage is NOT the driver turning "on". It is a DC bias that is sent to
the solenoid on the control wire. Which, by the way, is actually there all the time. You just will not
see it on a normal good working circuit. This bias voltage is used by the PCM to test the circuit for
opens and shorts . If yo u know the system uses a bias voltage , it can be used for easy
conformation of wiring integrity between the solenoid and the PCM .
•
Additional testing that can be done on this type of system:
Check voltage levels on both sides of the solenoid with the solenoid plugged in and un plugged
(d river off). With the solenoid plugged in, the ground w ire should read near zero volts, with the
control wire reading a few millivolts higher. (left picture) Unplugged, the control wire should
increase to around 1Ov. (right pictu re) What these readings indicate, is the integrity of the wiring
between the computer and solenoid is good.
~M
PCM
Solenoid
ii------'
rOv
Solenoid
100k ohm
- -(+)
resistor --+--i>
'------+~ll....oll~-1 2v
f
~~
Transistor Off
Voltage drop on the control wire only
occurs w ith the solenoid plugged in.
100k ohm
- -(+)
resistor --+-~
lli-1----
.l
Transistor Off
High voltage on the control wire is coming
from the resistor circuit not the driver.
26
Power Side Switched Circuit Problems
(continued)
PCM
,, ,...._
So lenoi d
t
t
Ov
0
Ov
Normal control wire "on" and
"off' readings, but the solenoid
doesn't function
0
,, ,......-
Trans s lo r Off
PCM
Sole noid
t
1 2v
t
1 2v
Only with the circuit "on" (loaded) can the ground wire
problem be seen. You must have the circuit "on" to
properly test a ground for a voltage drop problem.
- - 12v
T rans stor On
27
Variable Control Solenoids
•
There are two types of controls
1.
Pulse Width Modulation (P.W .M.)
•
This re fers to the on-time of a pulsed signal. (there is no comparison to any offtime period as with duty cycle measurements) It is usually measured in
milliseconds.
A longer pulse width will cause the solenoid to be "on" or "energized" for a
longer period of time.
•
0
A common PWM solenoid is a fuel injector. A longer pulse width causes fuel to
spray for a longer period of time.
Duty Cycle (D.C. 0/o)
2.
•
G
This refers to the percent of on-time within one cycle of a pulsed signal. (can also
be the off-time). Measured in a percentage ranging from 5°/o to 95°/o.
The higher the duty cycle 0/o the higher the current flow through the
solenoid winding, the stronger the magnetic field strength. This causes the
solenoid to open more.
•
A common duty cycled controlled solenoid is an idle air control motor. A higher
duty cycle causes the IAC pintle to open more due to a stronger magnetic field .
This raises the idle speed. (see Section 20 pages 23 & 24)
The terms pulse width modulation and duty cycle control have been used in describing solenoids
that are pulsed on and off to control solenoid magnetic field strength. There is some field
confusion as to which term applies to what component. What you need to understand is there
are similarities and differences. (see figure 12)
28
(Return)
Figure 12
PWM vs. Duty Cycle
1Hz Signal
500 m .s.
250 m .sl
0
In this picture you can see that if you change the pulse width you will change the duty cycle
and vice versa.
G
I I I I
I
I
I I
Ground side
switched circuit.
Low volts is "on"
and high volts is
"off'
In this picture there is a duty cycle change (0/o of on-time within one cycle) with no
change in pulse width (on-time in milliseconds). This is due to a momentary drop
or change in frequency. So you see there is a difference at times when measuring
these.
29
Fuel Injector Misfire Case Studfl"
8
Ford Taurus with a cam sensor problem causing the injectors to momentarily shut down
during a load condition. Symptoms where violent surging and misfiring under load.
Injector Duty Cycle
Injector Pulse Width
0
G
Typically there is no need to measure injector duty cycle but in this case it was the
duty cycle that showed the injectors where dropping out, not the pulse width. A
graphed pulse width reading may not show an injector "drop-out" if the pulse width of
the signal before and after the drop out are the same. A graphed duty cycle 0/o will show
30
the drop out as a sudden, longer 0/o of off time.
0
G
Oxygen Sensors and Fuel
Trim
Section 4
m'7 ~
Two Main Types of Narrow Range 02
Sensors
•
Zirconia 02 sensor
-
0
G
-
Creates it own
voltage
May or may not
contain a heater
circuit
Most widely used
type
Cheaper to produce
•
~
Titania 02 sensor
-
-
Variable resistor
Varies a reference
voltage supplied by the
PCM
Always a heated type
sensor
Becomes "active" much
faster than the Zirconia
type
Application is not
common
• Example: 1987-1990
Jeep
Output voltage is
reversed
2
Purpose
Narrow Range 02 Signal
•
-
The PCM "trims" the mixture by
adding and subtracting fuel from
this stoichiometric point
• For catalytic converter efficiency
0
•
02 Signal is used in closed loop
only
-
0
•
•
1.0
Feedback to the PCM, for
stoichiometric fue l control (all
upstream sensors)
Open loop the signal is ignored
(cold engine, WOT , heavy
acceleration, deceleration etc.)
May also be used for A. l.R. (air
pump) and EGR (exhaust gas
recirculation) system diagnostics
OBD II (1996 and newer) systems
use a "downstream" 02 for
catalyst monitoring
Rich
450mv --- Set
point
Lean
0 '--~~~~~~~~14. 0
14.7
15.0
Air/Fuel Ratio
3
02 Locations
B1=Bank1
This is the #1 cylinder
side of the engine.
B2 =Bank 2
Opposite bank of the
#1 cylinder
0
0
S1 =Sensor 1
Upstream (in front of
the cat.) fuel control
02
S2 =Sensor 2
Downstream catalyst
monitor(behind the
cat. unless there is an
Bank 2
83 02 sensor)
Sen s or 1
Bank 1
Sen sor 3
Bank 2
Sen so r 2
B a nk 1
S ensor 2
Bank 1
Sen sor 1
Bank 1
Se n sor 1
Bank 1
Sen sor 2
· B a nk 1
Se n sor 1
Bank 1
Sen sor 2
Bank 1
Se n sor 3
4
Open vs. Closed Loop
•
0
0
•
Open Loop
02 sensor is not being
used
Preset a/f ratio based off of
other inputs
PCM is not trying to
maintain stoichiometric a/f
ratio
Open loop occurs:
1. Cold engine
2. WOT
3. Heavy acceleration
4 . Deceleration
5. Extended idling
6. Initial start up hot or cold
7. Fixed rich or lean 02 signal
causing a fault code will
force open loop (see pg. 11 JI
•
Closed Loop
02 sensor is being used
- Preset a/f ratio based off of
other inputs is now being
"trimmed"
- PCM is maintaining a/f ratio
a little above and below
stoichiometric point
•
Closed loop occurs:
1. 90% of driving conditions
5
Operation (zirconia)
•
Sensor must be hot to work (minimum 600 °F)
Heated by exhau st gas (single wire sensor)
•
Sensor location must be near the exhaust manifold .
Heated by an internal heater circuit (3 or 4 wire sensor)
•
•
•
•
0
G
•
•
•
•
•
Allows for location of the sensor to be moved anywhere in the exhaust system.
Allows
. . the computer to enter closed loop mode faster which improves warm - up
em1ss1ons.
Signal output is from 0 to 1 volt with a typical range of 200 to 800mv
The mid point of the sensor range is 450mv which is the stoichiometric
window. Also known as the "set point".
Voltage higher than 450mv is read by the computer as a rich signal.
Voltage lower than 450mv is read by the computer as a lean signal.
Signal voltage should drop to at least 200mv on the lean side and
increase to at least 800mv on the rich side. (closed loop only)
Signal voltage should switch between rich to lean or lean to rich in less
than 1OOms or a frequency of 1 to 5hz. (closed loop only)
Typical 4-wire heated 02 wiring (sensor side)
1.
2.
3.
4.
White = heater (+)
White= heater(-)
Gray = 02 ground
Black = 02 signal
Black = Heater (+)
Black= Heater(-)
White = 02 ground
Blue = 02 signal
6
Understanding ST/LTFT
•
STFT (short term fuel trim)
•
- #1 job is to keep 02 sensor near
stoichiometric (a little above and below)
Is a command from the PCM to alter
injector pulse
- 0°10 = no fuel corrections from factory
preset value
Is only used in closed loop
NOTE* With left and right bank
upstream 02 sensors, the
PCM uses left and right bank
STFT & LTFT (individual
bank fuel trim control)
0
G
L TFT (long term fuel trim)
- #1 job is to keep STFT as close to Oo/o as
possible and to retain any corrections in
memory.
PCM "looks" at LTFT first to know where
to start injector pulse width
Learns from STFT%
Is a command from the PCM to alter
injector pulse
- Oo/o = no fuel corrections from factory
preset value
- +/- 1o % is considered normal on most
systems
May be used in both open and closed loop
Total fuel trim is the sum of the LTFT and STFT
Pre-OBDll GM used
http://www.youtube.com/watch?v=oRX2V6 a3do
Block Learn (LTFT) and
.
·
NORMAL :
Integrator (STFT) binary SUBTRACTIN G FUEL
RANGE •
ADDING FUEL
126
numbers. 128-= 0°/o....,.._1--.....-=.-..-..-..--.=---~
-----------------o1•~
o
•
;..
I
255
COUNTS :
26
~1
77
102
116
138
154
179
205
230
· 80".4
· 60%
-40%
· 20%
· 10'Yo
+ 10% +.20.04
+40%
+60%
+80%
PERCENTAGE
· 100%
I
+ 100%
0%
I
NO ADJU STMENT
7
m'7 ~
~
Bank Control Fuel Trim Example
4
0.0
9.4
Injector Pw'M Bank 2
Long Term FT Bank 1
Long Term FT Bank 2
....r
, ~
- ""'-
-
.-
Short Term FT Bank 1
,r- ~
0
G
%
: 8.6
--r
-
0.8
%
J
%
-
-
r
IAC Motor Position
Engine Speed
Desired I die Speed
Engine with a vacuum leak on Bank 2.
' 845
mV
107
mV
'' 854
''
' 93
0
904
640
cnt
-
-
'
' -2 .3
''
' 80
578
~
'
' -2 .3
: 8.6
3.9
-
H02S Bank 2 Sensor 1 v
%
___,..,.,.. - ........
Short Term FT Bank 2
H02S Bank 1 Sensor 1 v
msec
v
rpm
rpm
IAC Error OTC, no Fuel Trim OTC .
See section 20 for /AC count interpretation
8
02 and Fuel Trim ExamplelOJJ"
0
G
1994 CHRYSLE R CAR AA
A/T
3.0L V6 MPI
A/C
51 sustained LEAN F/A CON DITIO N
704 02S(V)_ 0.04 INJ(mS)_ 3.5
0 RPM
3 IGN CYCLES 2
134
IGN CYCLES 1
IGN CYCLES 3
0 OPE N/CLSD
LOO P CLSD
MAP SNSR(V)
1.2 MAN VAC("Hg)_ 19.2
BARO PRES("Hg)_28 .9 TH ROTTLE (o/o)
0
TPS(V)
0.82 MIN TPS (V) _ _ 0.82
2.3 COOLANT(°F)
199
COOLANT(V)
ST ADAP( 0/o)
24.8 LT ADAP( 0/o)
24.8
EXHAUST
LEAN VEH
0
SPEED (MPH)
8
• What is the 02 signal
indicating? Lean
• What is the computer's
command? Rich
• Is the 02 lying? Further
testing is needed. Perform the
following:
- Add propane to the intake
- Compare 02mv with tailpipe
C0 °/o
- Rapidly pump the throttle to
drive the mixture rich and
watch 02 response.
(see section 5 for more details)
9
m'7 ~
What's wrong with the fuel trim?
~
Scan data capture after repairing a vacuum leak without clearing PCM memory.
0
G
02Sensor111 Volts
0.85
02Sensor112 Volts
0.67
Long Term FTBank 1
24.2
Short Term FTBank 1
·25.0
Engine RPM
782
Throttle Position
15
Engine Coolant Temp
149
v
v
rpm
degF
This car is fixed! The PCM is simply in the process of relearning its fuel trim
memory.
Use ST and LT fuel trim numbers after a repair to determine if the problem is fixed .
Remember total fuel trim is the sum of both ST and LT and should be with in +/-10°/o
Example of where you fixed a problem but not all of it:
LTFT 35°/o STFT -15°/o Fuel Trim Total 20°/o ..... .keep looking, you still have a lean
condition. Its better but still not a fix.
10
m'7 ~
~
Fuel Trim Example With A Shorted 02
Integrator= STFT and Block Learn= LTFT (128=0o/o)
These are pre OBD II GM terms.
lor.p Stalus
!lJsed
'
'
'
'
~ Pulse WJJ!h
lor.p Stilus
6.9
4
msec 0
''
'
'
'
OCkleamMul
0
G
Open
6.9
~ Pulse Width
3
160
128
100
''
'
m!fl: 0
160
b:k le~nMul
lfll
160
128
160
'
rle~alo1
'
128
100
''
'
'
J2Ydt~e
rlega~o1
128
078
0.14
v
0
128
078
2Ydlage
0.13
v 0
Notice the change in fuel trim and injector pulse width when the system switches back
into open loop.
This is an example of an engine that runs better with the check engine light ON!
For this system (pre 080 II GM) to set an 02 OTC, the signal must stay fixed for 8 minutes!
11
Fuel Trim Numbers At Different Loads
•
•
0
•
G
•
Every Load/RPM combination has a learned LTFT number in
memory. By changing throttle angle and RPM while watching fuel
trim numbers you can determine the type of lean condition.
An engine with a lean condition caused by a vacuum leak may have
high fuel trim numbers at idle and normal fuel trim numbers at a
higher RPM.
An engine with a lean condition caused by a dirty MAF sensor or
low fuel pressure may have normal fuel trim numbers at idle and
high fuel trim numbers at a higher RPM.
To determine type of lean condition, run the engine from idle to
3500 RPM and note fuel trim values.
http://www.youtube .com/watch?v=n YN-RoFVwAA
http://www. youtube .com/watch?v=Sq pelz3aTNq
12
Vacuum Leak At Idle
0
0
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1998 C HEV ROLET
A/C
3.4L V6 CHEVY SFI
A/T
** CODES & DATA. OK TO DRIVE. **
(NO CODES AVAILABLE IN THIS MODE)
RPM_873 TPS(V)_ 0.51 TPS(o/o)_ _O
OPEN/CLSD LOOP_CLSD INJ PW(mS),_ _3.2
02B1-S1(mV)
39 02 B1-S2(mV)
4
ST TRIM( 0/o)
27 ST TRIM
163
LT TRIM( 0/o)
22 LT TRIM
156
RIGHT CROSSCNTS
0 02 READY
YES
MAF(gm/Sec)
2.88 MAF(Hz)
1858
MAP(V)
2.58 MAP("Hg)
17 .1
BARO(V)
4.80 BARO("Hg)
29.9
COOLANT(°F)
199 INTAKE A IR(°F)
99
IAC POSITION
20 DESIRED IDLE
725
13
Vacuum Leak At 1500 RPM
•
•
•
•
•
0
0
•
•
•
•
•
•
•
•
•
•
1998 C HEV ROLET
A/C
3.4L V6 CHEVY SFI
A/T
** CODES & DATA. OK TO DRIVE. **
(NO CODES AVAILABLE IN THIS MODE)
RPM_1554 TPS(V)_ 0.57 TPS(o/o)
2
OPEN/CLSD LOOP_CLSD INJ PW(ms)
3.1
02B1-S1(mV)
30 02 B1-S2(mV)
4
ST TRIM( 0/o)
27 ST TRIM
163
LT TRIM( 0/o)
22 LT TRIM
156
RIGHT CROSSCNTS
0 02 READY
YES
MAF(gm/Sec)
4 .70 MAF(Hz)
2331
MAP(V)
1.48 MAP("Hg)
11 .1
BARO(V)
4.80 BARO("Hg)
29.9
COOLANT(°F)
225 INTAKE A IR(°F)_ 106
IAC POSITION
26 DESIRED IDLE
700
14
Vacuum Leak At 2500 RPM
0
0
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1998 CHEV ROLET
A/C
3.4L V6 CHEVY SFI
A/T
** CODES & DATA. OK TO DRIVE. **
(NO CODES AVAILABLE IN THIS MODE)
RPM_2521 TPS(V)_ 0.70 TPS(o/o)
5
OPEN/CLSD LOOP_CLSD INJ PW(ms)
2.9
02 B1-S1(mV)
299 02 B1-S2(mV)
556
ST TRIM( 0/o)
13 ST TRIM
145
LT TRIM( 0/o)
22 LT TRIM
156
RIGHT CROSSCNTS
6 02 READY
YES
MAF(gm/Sec)
7.95 MAF(Hz)
2927
MAP(V)
0.96 MAP("Hg)
8.3
BARO(V)
4.80 BARO("Hg)
29.9
COOLANT(°F)
210 INTAKE AIR(°F)_ 113
IAC POSITION
28 DESIRED IDLE
700
15
Vacuum Leak At 3500 RPM
0
0
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1998 C HEV ROLET
A/C
3.4L V6 CHEVY SFI
A/T
** CODES & DATA. OK TO DRIVE. **
(NO CODES AVAILABLE IN THIS MODE)
RPM_3472 TPS(V)_ 0.88 TPS(o/o)_ _ 11
OPEN/CLSD LOOP_CLSD INJ PW(mS),_ _3.2
02 B1-S1(mV)
334 02 B1-S2(mV)
595
ST TRIM( 0/o)
-2 ST TRIM
126
LT TRIM( 0/o)
11 LT TRIM
142
RIGHT CROSSCNTS
9 02 READY
YES
MAF(gm/Sec)
14.89 MAF(Hz)
3779
MAP(V)
1.00 MAP("Hg)
8.5
BARO(V)
4.80 BARO("Hg)
29.9
COOLANT(°F)
22 1 INTAKE A IR(°F)
97
IAC POSITION
42 DESIRED IDLE
700
16
Dirty MAF At Idle
Throttle Position
11
%
Engine RPM
890
rpm
Long Term FT Bank 1
·3.9
%
Long Term FT Bank 2
0.8
%
Short Term FT Bank 1
1.6
%
0
Short Term FT Bank 2
0.8
%
Mass Air Flow.
4.63
g/s
0
Malfunction Ind Lamp
On
Engine Coolant Temp
71
degC
Vehicle Speed
0
kph
Spark Advance
16
deg
Cale EngineLoad
17.3
%
DTC's Set
1
17
Dirty MAF At 2500 RPM
Dirty MAF At 3500 RPM
EGR Flow Test Using The 02 Sensor
The PCM monitors EGR flow on
some systems by watching 02 and
STFT while turning the EGR on and
off at different times during closed
loop operation.
0
G
Chrysler Backpressure
EGR System
Backpressure Transducer
EGA Solenoid
How much STFT o/o changes is
dependent on how much EGR flow
occurs.
EGR commanded on during cruise
would cause the 02 signal to go
rich and STFT 0/o to drop.
EGR commanded off during cruise
would cause the 02 signal to go
lean and STFT 0/o to increase.
Notice this system does not have
any type of EGR flow sensor. Only
a solenoid and a backpressure
transducer.
20
AIR System Flow Test
0
CD
The PCM tests the air
pump for proper flow by
turning on the pump in
closed loop and then
watching 02 and STFT.
A good air pump causes
the 02 to drop lean and
STFT to increase to a
pre-determined amount.
Air injection
bypass solenoid
LH exhaust
manifold
-Vacuum
source -
Solid state
relay
RH exhaust
B+
manifold
-LJ
r Electric
•
air
pump
Air
pump
LH catalytic
converter
Air divert
valves
(AIRD)
RH catalytic
converter
21
Oxygen Sensor Testing
0
0
Section 5
Oxygen Sensor Signal Circuit T.mtffig ~
All detailed 02 testing must be done off idle with a hot sensor.
•
•
0
G
•
Scan Data
• Look for a min. of 200 - 800 mv.
• Frequency cannot be determined because scan data reports over
frame, not time. Speed up your data process by limiting data PIDs
to see if the 02 is switching rapidly.
DSO
- Connect scope(+) to the 02 signal wire and scope(-) to a known good
ground or 02 sensor ground
- Set scope on a 5 second screen with a 2 to 5 volt scale
• Look for a min. of 200 - 800 mv.
• Look for a frequency of 1 - 5 HZ.
- OBD 11 systems look for a switch rate from lean to rich and rich
to lean in less than 100 m.s. (alternate frequency test)
(figure 1)
Digital Voltmeter
- Look at the signal as you would on scan data (due to the slow sampling
speed of the DVOM you cannot accurately measure frequency)
nttp:fiwww.youtube.comfwatCh?v=u MGnvtgf8w
2
(Return) Figure 1
x=l SS'ims,.o -=1 bU!Jfn s~
0 .8
0.6
n.•
0 .2
1.0
n.n
•••
•0.2
II
II
..o..ii
11
11
11
11
11
0.6
n.o
1.0
0
0
O. G
•••
0 .2
II
II
II
..o.o
0.5
1.0
I . !i
After
re p lacing
both 0 2s
2.0
2.5
3.0
3 .5
Cursors set at 600 and 300mv
for ric h to lean switc h t ime
measurem ent
v
' .o
O. R
Blue trace
setting " 02
1.•s1ow respo n se
•••
0.A
n.nDTC "
•••
J
o.n
O. G
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. . ..
0.A
0 .2
•O.G
o.o
. .o.o
-0 .2
.., . 0
u.u
U.b
1 .u
1.b
2.U
2.b
~. u
•.u
•••
- t) , 4
b.U
•
3
02 Signal Fixed Rich
(above 450 millivolts)
•
0
G
Ask you rself, is the a/f ratio actually rich or •
is the sensor lying?
1. Make a large vacuum leak
Signal voltage should drop to below
175 mv in less than 100 m.s. If it does
you must find the cause of the rich a/f
ratio . The 02 sensor is not the
problem!
- If signal voltage stays rich the sensor is
lying or the a/f ratio is extremely rich.
Perform the test below to confirm.
http ://www.youtube .com/watch?v=H61Y 42u 19VM
1. Compare tailpipe C0°/o to 02 sensor
voltage cfigure 2)
- If 02 mv is fixed rich and C0°/o is high
then the 02 is NOT lying. Look for the
cause of the rich a/f ratio. The 02 is
NOT the cause!
- If 02 mv is fixed rich and C0°/o shows
normal to low, the sensor is lying
(check 02 heater circuit and 02 signal
and ground for opens and shorts
before replacing 02)
See page 6 for tailpipe CO review
Causes of a rich exhaust, negative
fuel trim numbers and/or higher
than normal 02 mv
- Higher than normal fuel psi
- Ruptured fuel psi reg. diaphragm
- Leaking fuel injector
- EVAP purge problems
- ECT or IAT sensor problems
- MAP/BARO or MAF sensor
problems
- EGR va lve stuck open at idle
- Fuel contaminated oil
- Head gasket leaking causing
coolant contamination of the 02
- Jumped timing chain/belt
4
02 Signal Fixed Lean
(below 450 millivolts)
•
1.
0
G
2.
Ask yourself is the a/f ratio actually
lean or is the sensor lying
Add propane thru the air intake
(enough to hear an rpm change)
Signal voltage should increase to
over 800 mv in less than 100 ms.
If it does the sensor is not lying
and the a/f ratio is actually lean
If signal stays lean the sensor is
lying
Compare tailpipe C0°/o and 02°/o to
02 sensor voltage lff1gure 3)1
If 02 mv is fixed lean and C0°/o is
low with high exhaust 02°/o, the
sensor is NOT lying. Look for the
cause of the lean a/f ratio.
If 02 mv is fixed lean and C0°/o is
high, the sensor is lying. (check
02 heater power and ground and
02 ground before replacing 02)
see pg. 10
•
Causes of a lean exhaust, positive
fuel trim numbers and/or lower than
normal 02mv
- Lower than normal fuel psi
- Vacuum leaks
- Clogged injectors or injectors not
firing
- Contaminated fuel
- ECT or IAT sensor problems
- MAP/BARO or MAF sensor
problems (especially a dirty hot-wire
type MAF)
- Jumped timing chain/belt
- Exhaust leaks upstream of the 02
(false lean, causing rich a/f ratio)
- Severe misfiring (false lean,
causing rich a/f ratio)
- AIR system problems (false lean,
causing rich a/f ratio) (figure 4)
http://www.youtube.com/watch?v=G 89r12vZFVJ
5
(Return)
Five Gas Theory
Efficient Air/Fuel Range
C0°/o is your rich
0
G
indicator. You will not
read carbon
monoxide on the
lean side of
stoichiometric. Use
tailpipe C0°/o levels
to determine how
rich the engine is
running or if a fixed
02 sensor signal is
reporting accurately.
02°/o is your lean
"
i!l::iJ~r ~
10/1
indicator. You will not
read oxygen on the
rich side of
stoichiometric unless
it is coming from
outside of the
combustion
chamber. (false lean)
15/1
20/1
AIRFUEL RATIO
6
(Return)
Figure 2
1.6 ~-----------.-------\)
. . ...
.
12
•
•
•
0
G
Look at C0°/o and 02°/o, is
the engine running rich,
lean or normal?
Compare these readings
with 02mv .
Is the 02 sensor lying or is
it indicating the proper
mixture?
. .
. . . . . . . ..
..
··· ··· ··· .· · · · · · · · · · · · ·
.
. .
, , , , , ... . .
.
.
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...
...
.
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.
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.
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.... . You :w.ill
.not.ha.ve
.a.fixed
.
.
. rich 02:. in .a .....
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'
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o ..... zero. co.environment..This
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. . . . . . . . . :. . . . . . . . . . :. . . . . . . .
'
a
.:
:
:
'
-o.4 0
1
2
rs.incl Si al
Paltern/Swee Scale
ILock I Pi npt 1
5 sec
2 u
:
'
4
s
5
l-,!t1~ov!.!.i!:...e-1-~Cu~rs~o!;...r_
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1. ~,-th~
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, ----.---. ---....:;
-.:.:_-:...:-...:..
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u 6
se
y1ng .;
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. : . . . . . . . . . : . . . . . . . . Ud . PP" . . . 601
:
co :I.
10 .7
1.2 .. .. . .... : . . . . . . . . . : .. . . . . . . . : . . . . . . . . oi .;1, . .. ..0.. 2
6.7
-10.. 0
You will not have a fixed lean 02 in
o.s · · · a 10. 7°/o CO environment. This is a
· · · dead 02.
0. 4
.
. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .
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.
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0.2
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z
1
" " " ' IC'
3
Scale
Pattern/Sween
Si anal
Pi n...,, t.
.
1
5
sec
2
v
.
. .
4
Disnl a~
Aut.o
Tr
7 ~
(Return)
Figure 3
-v. -
.
.
. . .. . . .
.
. . . . .
..
0.8
After
replacing
0 .6
02
0.4
... .
. .
. .
.
. . . l:IC . PPM . . . . 15
x
.x
cft x
11
"" " ··
.
.
· Raio
0. 0
. .o. .
14 .
1:4".
.
. . . . .
. .. . .
. . . ... .
.
0 .2
. . . . . .. . . . . . . . . .
D o ~~~~~,.1--<-~~~~-::f---~~~~""";f-~~~~-'-7-~~~~~
D
O
0
b·b
G
0 .8
02
2
3
- 4.
s5
.--~
ls~t~
he~o
=2~1~
yin
-g~
?: ~~~~~~~~~~~~~~~~. ~~~~--.
1 .2
Before
replacing
1
0 .4
0
D
D
-o.4 n
. . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . l:IC . pp111 . . . .601
.
.
:
c~ x
10. 1
· ·Th·is extremely rich exhaust·was caused · · · · 0 ~ · :..c • · · · •0 ·· 2
:
:
1
2
.
C02 x
6. 7
· ·b y·an 02· reporting l e~n · a ll· the· time: · · · · · · · ~i · ~~~io · t:g·:g
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
.
.
''
. . . . . . . .. . . . . . . . . . .' . . . . . . . . ' . . . . . . . . . .. . . . . . . . . .
..
.
.
. . . . . .
.....
.... ..... .....
. . . . . .. . . . . . . . .
. . . . . ..• . . . . . . . . . . . . . . . . . .
...
•
.
•
. .. . . .
. . . .
. .. . . . . . . . .
...
3
4
s
8
(Return)
Figure 4
02 signal with air pump off
•
••
•
••
•
0
5s
0. 0931J
02 signal with air pump on
1
1
0
0
0. 21 5 1JDC
5s
0. 6681J
0. 8 51 1JDC
1988 Chevy Camaro 2.8L Failed PA State Emission Test
(Limits for this year car: HC 220 C0°/o 1.2)
G
Em ission levels are
now good but the fuel
trim numbers are too
Iow . This was due to
fuel contam inated oil
from a n exte nded
period of time that the
.
.
engine was running
rich .
Tailpip e Rea dings A fte r
Ta ilp ipe Readings Befo re
'"'
H""C- - - - - =4'-"P:::.cP:..:..m:..:-_ _ _ _ _-=9:;.;:5:..1P""P::.:.m
!!.
co
Why is the PCM
.5 •1.
4 .5- 5 .3 •1.
.:
C..:::0-=
comm anding rich (high
010
2_ _ ____,_
1 :::..:
3 ·c:.
5-'.;."-._ _ _ _ _ _.:.
9 ·:..::9~
02
block lea rn) when the
1 . 0 •i.
3 .8 •i.
.:...:::;----~'--'-"------..:=.:.~
!!.In'""te""'g..,,r.::.at.:..::o:..:..r_ __,_
1..:.;
14;!..-_,_1::,,
2 2::...__ _ _ _ _1.:..::3:..=.
2 , ~-_.-'\ ex ha u st is a Iready rich
Block Learn
11 5
1 52
as indicated by high
C0°/o? Th e air pump
problem caus ing a
false lean condition
9
02 Signal voltage fixed with Wo
response to ratio changes
•
Possibilities
G
Tests used
- Bad 02
- Verify bias voltage (some)
- Short to ground in the
signal wire
- Ohmmeter
- Open in the signal wire
0
•
8
- Voltage drop tests
- Heater circuit problems
PCM response testing
(some)
- Sensor ground problems
- Scan data response testing
- Computer ground problems
10
m'7 ~
~
02 Sensor Signal Bias Voltage
•
•
•
•
0
G
The PCM sends a small bias voltage to the 02 sensor.
With an active 02 sensor the bias voltage gets pulled up and down with the 02
signal.
Can only be measured with a cold sensor or with the sensor unplugged .
Cold sensor = very high resistance to ground = high bias voltage
Hot sensor = lower resistance to ground = low bias voltage
02 Signal wire bias voltage levels
1.
GM = 450mv bias
2.
Chrysler = 500mv bias with a warmed up sensor and a 5v bias with a cold
sensor
3.
Nissan, Honda = similar to GM 400-500mv
4.
Ford = no bias
NOTE: Scan data bias will be higher than what you will read with a voltmeter. This
is because the bias voltage is so weak that even a 1OMohm impedance meter will
pull the bias voltage down a hundred millivolts or so.
•
Purpose of signal wire bias voltage
1.
Allows the PCM to monitor a non computer controlled 02 heater circuit.
2.
Used by the PCM for proper AD (analog to digital) converter operation
Any circuit that has a bias voltage can be easily checked for opens or shorts
without using an ohmmeter. Just unplug the sensor and measure the
bias
voltage. No bias voltage means there is an open or short in the
•
wire.
11
m
(6\i
r=1
'V :
:
(1(AJ
02 Sensor Signal Wire Bias Voltage Testing
•
Scan data test
1.
2.
0
G
3.
Scan Data 02mv signal fixed at 0
Disconnect 02 sensor connector and recheck 02mv Pl D
•
1. 02 now reads around 450mv (GM) means the signal wire from the
PCM to the 02 sensor is good and the sensor is bad
2. 02 signal is still fixed at 0 volts means the signal wire is shorted to
ground
Scan Data 02mv signal fixed at 450
Jump the signal wire to ground at the 02 connector using a test light
•
1. 02 PIO now read Ov =bad/open 02 sensor
2. 02 PIO stays at 450mv =open 02 signal wire
lh ttp://www.youtube.com/watch?v=adkFTSoxM6Q (GM)
02 signal fixed high (up to 5 volts) - (Chrysler)
Caused by an open in the 02 sensor, the 02 sensor signal wire, the 02
•
sensor ground wire or a heater circuit problem
http://www.youtube.com/watch?v=v8XrM-7Bu0g (Jeep)
•
Measure signal voltage at the sensor
Voltage at the sensor matches scan data = bad 02 or heater circuit
not working (check heater + and -)
Voltage at the sensor differs from scan data = open signal wire , bad
02 sensor ground or PCM problem
(most common problem is just simply a bad 02 sensor)
12
JfYll """""
l.!..LJ.J'V : :
Col"l
<i[8J
Signal Wire Bias Voltage Test (case study)
http://www.youtube.com/watch?v=nlhqTGOiBVU (Honda)
Signal measured at the sensor back probing harness side
I
I
02 signal
1
I
02 signal shorted
I
I
I
0
G
02 signal , sensor unplugged
What does this tell you
about the 02 signal
wire from PCM to
sensor?
Its good! Leave
your ohmmeter in
your toolbox.
0
The concern during this period of low voltage on the 02 sensor was either the sensor is bad or the
signal wire is shorted to ground. Unplugging the sensor and using bias voltage was the key.
lM
13
m ...,. ~
02 Sensor Ground Bias Voltage~
0
G
•
Newer systems use a bias voltage on the sensor ground.
•
Improper diagnosis of the 02 sensor will result if this is not taken
into account.
•
Purpose of a ground bias
1.
Improves accuracy
2.
Eliminates ground circuit interference problems
3.
Proper AD converter operation
14
1997 Volvo 02 Ground Bia§OJ~ ~
. . . . .: ·
l
.
..... . ...
.6 .................... . .
..
..
. . . .....
,
.. . .
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. .This. W;as taken ~fter relo cating tht3 ·
1
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·
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.
Notice the 02 signa amplitude is higher
.
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1997 VW 02 Ground Bias ffi~
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1 4~------~------ ~ --the wrong ground connection during the test
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2.5
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3.5
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Scope (-) lead on battery negative
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1.5
4.5
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02 Sensor ground bias voltage was .3 Volt
16
2004 Dodge Stratus Case StuWys
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:
Notice the 2.5 volt bias on the 02 sensor ground and what it did
to the amplitude on the signal wire.
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17
<=>
L.:..l4J'V : :
2004 Dodge Stratus Case Stu
02 Voltage OEM Scan Data
02 Voltage SAE Generic Scan Data
3.39.
0.84 .
3.35 .
0.8 .
3.3
v
0.75 .
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3.25 .
0. 7
3.2
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3.15
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3.05.
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2.8
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2.75
2.7.
2.65
2.6 .
2. 56
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0.15 .
Scan Data captures of a normal 02 sensor signal using two different methods
of communication. Once again you must be aware of the 02 sensor ground
1a
circuit desian
m'7 ~
~
02 Heater Circuit Description and Operation
•
OBD-11 systems require 02 sensor heater circuit monitoring. This can be
done in the following ways:
1. The PCM directly controls the 02 heater power or ground using a
transistor. With this method the PCM can monitor voltage levels and
current flow through the heater circuit directly.
• If voltage or current levels do not match what is desired a trouble
code is set and the heater circuit may be switched off. This may
cause inaccurate diagnosis of the heater circuit.
-
0
Example: A ground side switched heater circuit reads battery voltage
on the heater ground. This leads you to believe the transistor inside
the PCM is bad (not turning on) but what is really happening is the
PCM doesn't like what it "sees" on the heater ground circuit so it
switched the circuit off intentionally. (see section 3 for further info)
2. The PCM monitors the heater circuit by using a bias voltage on the
signal wire. With the sensor cold the bias line voltage is high (due to
high internal resistance of the 02). At start up the PCM watches the
bias voltage drop (as resistance drops in the 02) to determine heater
circuit activity. htfp:ffwww.youtube .com/Watcn?v=v8Xr~Bu0g[ (Jeep)
G
•
The 02 heater circuit may also be pulse width modulated (PWM) this must
be taken into consideration when using an average reading digital
voltmeter. You will read lower than normal power and higher than normal
ground voltage. (see page 22)
19
02 Heater Tests
•
Voltmeter or Scope
-
0
G
KOER, sensor plugged in, backprobing 02 connector
Connect one lead to a known good ground and the other lead to the heater (+)
wire and the heater (-) wire individually
• Heater(+) should equal system voltage (most)
- Some PCMs will PWM the power side of the 02 heater.
» Voltmeter tests will show lower than normal feed voltage if PWM
is used (average read ing)
• Heater(-) should be close to BAT(-) (around 300-400 mv)
- Some PCMs will PWM the ground side of the 02 heater.
» Voltmeter tests will show higher than normal ground voltage if
See pg.21 and
PWM is used (average reading).
22 for Scope
• During initial start up, some systems delay the turn on of the heater on
examples
downstream 02s to allow time for moisture burn off.
• Also the heater circuit may be "turned off' if the PCM recognizes a fault in
the heater circuit. (I ncorrect voltage level or cu rrent flow on the heater control
wire)
•
Inductive low current probe testing
-
•
KOER, sensor plugged in.
• Measure amperage on either the heater + or - wire.
• Can read anywhere from 600 ma to over 2000 ma
Scanner
-
Some systems will show 02 heater current draw on data stream
20
PCM Controlled 02 Heater Growntt
(Not a PWM type)
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power feed)
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2
4
6
8
10
12
14
16
18
20 s
21
PCM Controlled 02 Heater P'1Ner
(Return)
(PWM type)
' File
Edit
Settings
Vle¥J
Window
Automotive
Help
g jg~ ~ xj 100 m s /div :::J jx1
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8
If monitoring this power feed with a
.
voltmeter, you would read around 7
5} - volts and might think you have a
4' - - - problem
4
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0.0
J Waiting for ADC
0.1
0 .2
0.4
0.5
0.6
o.7
A = 02 Heater Ground B = 02 Heater Powe r
C = 02 Heater Curre nt (idle, warm engine, known good)
Heater circu it is power s ide s witch ed and grounded to blo ck
0. 3
0.8
0 .9
1.0 s
·"""lJ.__...:::J...._.IJ_ __jJ_.] 1450
Trigger .J_N_o_ne_ _.:...
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22
PCM response testing
Engine at normal operating temp above idle speed.
Scan data 02 signal will change during this test however injector pulse width and RPM
may not if the system is in open loop.
• Simulate a rich signal
0
G
- Touch one hand to battery(+)
and the other to the 02 signal
wire. (Sensor may need to be
plugged in for this test to
work)
- Scan data 02 mv should read
over 1000 and the PCM
should respond by decreasing
injector pulse width (STFT 0/o
should go negative)
- C0°/o should go down
- RPM will change
• Simulate a lean signal
- Test light connected to
battery (-)
- Touch test light to the signal
wire. (Sensor may need to be
plugged in for this test to
work)
- Scan data 02 mv should
drop to zero and the PCM
should respond by increasing
injector pulse width (STFT o/o
should go positive)
- C0°/o should go up
- RPM will change
The above testing is used to quickly identify signal circuit integrity
(no opens or shorts) on 02 sensors with no bias voltage.
23
m
Downstream 02 and Catalyst Oxygen Storage
(6\i
r=1
'V :
:
(1(AJ
Tests
Good Oxygen Storage
1O Downstream Switches
400 Upstream Switches
= 0 ·025
- - - - - ----------- --- -
Poor Oxygen Storage
0
G
300 Downstream Switches
400 Upstream Switches
Upstream 02
1.0 Volt
Pre-Cat
Post-Cat
Good Ox gen Storage
= 0.875
Downstream 02
Delayed
Reaction
by Post-Cat
Sensor
~
O . . . Time in Seconds
...
25
Poor Oxygen Storage
0.0 Volts
- - - - - ----------Post-Cat
Sensor
Mirrors
Pre-Cat
24
Catalytic Converter Oxygen StoragJlt~t
Bad Cat. Setting P0420 OTC
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5
Catalytic Converter Oxygen Storage Test
Known Good Dual Cat. System
Edit
Set t ing:;
View
W indo w
Automotiv e
Help
31
3'
:::J loc3 Jx1 3
3
x = 17.00 s , o = 6117m s , xo= -10.88s
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o.o~;1!"!'~~~r.·~-~-r-~-~-~-~:-~-~-~~'.l!"l'~:li;,o~""'rrltit'~~~~~~~r:o~~~,,.,~.i.,!~~,...,;,..1+,1,o.:1- ····•········ ··· rt . 2
-0 . 4
- 1.6
0.4~
~ ~~~~'!';'~
-,!":I
.-~
--~
- -r-"-'!'1
, ~~~~~~~~~~"""
-0 . 4
-2 . 0
.
....
.
•••••··~··•••••••••••,•••••••••••••r••••••••••••r••••••••••••r••••••••••··~··••••••••••,
'
o.o
....
.
.....
. . .-. . . . . . . . .
..
..
-0 . 4~
Downstream
-o .e~
0
Waiting for AOC
.
2
Trigger
,
4
.
,
-·.
.
-
..
.
..
B
10
12
14
A = 02 61 S 1 6 = 02 6 251 C = 02 61 S2 0 = 0 2 6252 1<.0ER@
at idle d ur ing oxygen sto r age test . N ew cats on bott1 banks .
INone 3 I
6
31
3 ,_I•_ _,l~ mv
26
0 .4
m
-~
o.
<=>
'V : :
Can a downstream 02 look like an upstream
02 with a good Catalytic Converter?
v
v
2.0·····························-,······················································································································ ..........................................................., ............................................ ,.............. ,........................... '''
., ..i . . : : K.n9w:n G99d C~t-~lyti~ C..oo..v~rt~r . . . ... · ...........
1.2
2.8
0
G
.
.
.
.
.
.
.
' Cold
';
';
';
':
'; . • . • . • . Hot• • . ': • .
:
..
..
•
• . •
• . •
..
. -o •
..
.
.
.
.
.
.
.
.
.
.
.
.
.
..
...
..
..
...
..
1.6· ..........; ..............
; ......................... :.
: ......................... :..
........• .•......
........ . •......• .:........ ........
........ .......•
.....•.. . ...... :.
........ . ....... -O t
·
·
gets hot the signals will look the same !
·
.Until the. converter
.
1.2•
2.Q
0
...: ..
..
''
s
'
'
~.
I
'
!
10
15
20
!
!
!'i
30
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!
35
•O
•5
I
5
10
..'
15
ro
&
~
~
;
itO
itS
' ~1.2
Su ,
27
Thermistors
0
0
Section 6
Types of Thermistors
0
G
NTC
PTC
• Negative Temperature
Coefficient
• Positive Temperature
Coefficient
- Used as a temperature
sensor for a computer
system
Examples:
-
Engine coolant, intake air,
ambient air, transmission fluid, incar, evaporator core, high and
low sides of an AC system, EGR
flow monitoring, battery temp,
fuel tank temp, EVAP purge flow
etc.
Used in place of fuses on
some systems
• With normal current flow
through the system the PTC
thermistor has no resistance
so it will not affect circuit
operation
• With excessive current flow
the PTC thermistor will heat
up and increase resistance
which will reduce current
flow in the circuit.
2
NTC Thermistor
S ignal to
computer
•
0
G
1.
2.
Ground
S ignal for
gauge
Signal to
computer
Ground
Signal for
gauge
Description and Operation
Negative temperature co-efficient thermistor (NTC)
• As temp. increases, resistance decreases
Most are two wire sensors, one signal and one ground .
Some are three wire sensors, two signals sharing one ground .
The 5 volt reference wire on a thermistor!.§. the sensors signal wire and is
never shared with other inputs. (The computer "watches" what it is sending
out to the sensor)
The ground circuit is constant and may be shared with other inputs
• As temperature increases resistance decreases which causes the
applied 5 volt reference to drop.
Cold = high resistance= high voltage
- Hot = low resistance = low voltage
3
m'7 ~
~
Thermistor circuit operation
PCM
-----------------,
I
Constant 5v from internal
PCM 5v regulator
l
I
I
I
I
I
1
T hermist or
Signal/Sv 1"efe1"enc·e
I
I
Vol tage sensing cirouiL
Does not support
any measurable
amoun1 of current 110\v
I
I
I
I
4 .Sv cold
1 .0v hot
--,,_____ _________________________
___,
I
I
I
:
30,000 ohms cold
1 ,000 ohms hol
Signal retum (ground )
<100mv___.
I
0
G
Notice in the picture, as the thermistor heats up its resistance drops which pulls
the signal voltage down.
Note: Current flow on these types of circuits is in the micro amps and not
measurable, however there must be current flow for a voltage drop to take place.
In a thermistor circuit the computer is monitoring voltage between two resistors
in series. The "pressure" or voltage between the two resistors is dependent on
the amount of resistance of each resistor and whether or not there is a complete
circuit. If there is an open in the circuit there will be no current flow and therefore
no voltage drop across the resistors. This will cause the computer to read 5v all
the time. If the signal wire shorts to ground or the thermistor internally shorts, all
source voltage will drop across the first resistor. This will cause the computer to
read Ovall the time.
4
Thermistor circuits
PCM
Conventional
Thermistor
'\i fJ, f'* S,t,1iig} j:~,. 'iiJv.i,,., Ahn,i;,~ !::'*.
5Volt
Regulator
1.._.._ _,f--r--l
Variable betwee n 0-5v
Signal
::J l•c::J !OH ::J
v
5.0
<.S
..o
~
Thermistor
--------.....
Ground
'----~---1f--..L---'----i ll
G
E!l!':i!gij xlso '1d;v ::JI•• ::J •lsv ::J loc::J lo• ::J olo•
Think f
l .5
this a a
l .O,
.:-- ---r- hig h
l .S "
"'-•.................,
~_,__~ Voltage
im ped nee 2.0
............_ ___.._
I.'>
Sensing
v oltm ter
1.0
'--"T"'""--' Ci rcuit
~
0
~~
~
~-~·-~----
0.5
50
1DO
150
200
250
300
350
400
450
•
soo
Constantunder1 00mv
PCM
Dual Circuit
Thermistor
5 Volt
Regulator
f--r-l
v
5.0
120° switch point
4.5
•.O
5v re f. runn ing
through 1Okohm
resistor {cold cu rve)
l .5
l .O
l .S
i
----- - -
-~
Thermistor
Vo ltage Sensi g
Circuit
--~-......___ _ _
z.o
..--'-~
1.5
>---~
1.0
- - --
o.s
0.0
11
n
ID
50
WeldngferAOC
100
150
Triyyer INu111:
- --·
5v ref. running
through 1koh m
res istor {hot curve)
?,0 0
250
)00
)50
.:.I I
.:.I I
.:.1 EJa
"'
lu
4!i0
•
!iOO
~
Primarily used on ECT sensor circuits for better monitoring of the warm up period of the engine.
5
Dual Circuit Thermistor Operation
•
Ohms law review
E = I x R, I = E + R, R = E + I
E = Electromotive force (volts)
I = Intensity (amps)
R = Resistance (ohms)
•
0
G
Kirchhoff's Voltage Law
-The sum of all voltage drops in a circuit will equal the source voltage.
Use the above formulas in figure 1 to explain the following :
'
1. As resistance decreases in the external resistor the signal voltage will drop .
2. As resistance decreases in the inte rnal resistor the signal voltage will rise.
The external resistor is the thermistor and the internal resistor is switched from
a high to a low ohm resistor at approximately 120°F. With this design small
changes in temperature cause large changes in signal voltage. This allows
the PCM to more precisely lean out the mixture as the engine warms up.
- The "cold curve" runs the 5v reference through a 1Okohm resistor.
- The "hot curve" runs the 5v reference through a 1kohm resistor
6
m
(Return) Figure 1
(6\i
r=1
'V :
:
(1(AJ
In this illustration I am showing the source voltage as 12v for easy math. A thermistor circuit will use a
5v source, and is grounded inside of the PCM.
Inside of the computer
Inside of thecomputer
Outside of the computer
---------------------------1
A drop in resistance
here
Outside of the computer
-· This is where the computer
would be monitoring the circuit.
1ohm
'
1ohm
12v 11ohm
(1vd11e1i:
Ov
--,/'NV'\,.-____;.....,....+---....,/V'VV'1.,-----lll
E=12volts
(O vo11s 1e1t)
Rr=12 ohms
Ov
--,/'NV'\,.-~--.-..+--....,/V'VV'1.,-----ll l
(0 l'd1s left)
I=1amps
(11volt drop)
0
-
Equals a rise in voltage
' - - - - - - - - - - - - - - - - - ------< here
G
Inside of the computer
I
I
I
I
I
12v
I
(0 veils
(1veil drop)
I
I
I
(11Yols left) I
1v
I
A drop in resistance
here
11 ohm
E=12volts
Rr=12 ohms
I= 1amps
~ft) 11
12v
E=12 volts
Rr= 3ohms
I= 4amps
I
Equals a drop in voltage
' - - - - - - - - - - - - ' - - - - - - - - - - - 1 here
2ohm
Ov
(8voltsleft)I
(<hells left)
8v
(11\d ldrojl)
--
Outside of the computer
---------------------------1
---------------------------1
1ohm
Inside of thecomputer
Outside of the computer
(8veil drop)
7
II
Engine Coolant Temperature Senmr""
(ECT)
•
0
0
Description and operation
1.
Main input for cranking air/fuel ratio and warm up fuel curve.
The colder the engine the richer the ratio
2.
Input for electric cooling fan control
3.
One of the inputs for electronic climate control systems.
4.
5.
Indicates heater core temperature.
One of the inputs for idle speed control.
Cold engine fast idle speed.
Other outputs affected by the ECT input:
AC clutch, EGR control, AIR pump control, Spark timing,
Open/Closed loop operation.
- No AC during overheating
- No EGR on cold engine
- No AIR on a warm engine
- No closed loop below 150 deg.
8
Symptoms with a Faulty ECT
0
0
•
•
•
•
•
•
•
•
•
No start due to a flooded engine.
Overheating (electric fan only)
No cold fast idle
Start/stall
Hot engine high idle speed
Failed emissions
Black smoke
Lean hesitations (during warm-up only)
No AC clutch engagement
9
ECT Scan Tool Testing ffi~ ~
1.
2.
3.
4.
5.
0
G
6.
~
Compare ECT and IAT temp. on a cold engine
Should read within 5 deg. of each other
Compare engine temp. to scan data ECT temp.
Warm up engine and note ECT temp. when the cooling fans turn on. (210 to 230
deg.)
For intermittent ECT trouble codes wiggle ECT wiring and connector and watch for
changes.
Wiring test
Signal voltage fixed at Ov
•
Unplug ECT sensor
- ECT signal should rise to near 5 volts
- ECT °F should drop to near -40°F (Keep in mind the PCM will substitute
values on certain data Pl Ds) Section 11 "Substituted Values'!
Signal voltage fixed at 5v
•
Jump ECT wires together
ECT signal should drop to near 0 volts
ECT °F should read from 260 to 400°F
Use ECT data to check for a stuck open thermostat
Test drive car at a constant speed over 25 mph while watching ECT temp.
ECT temp. should not drop below thermostat rating.
A stuck open thermostat can cause poor gas mileage from extended open
loop operation, and will set a trouble code on some systems.
10
ECT Voltmeter Testing
•
•
•
0
G
KOEO or KOER (backprobing sensor connector)
Connect negative lead to a known good ground
Connect positive lead to :
1.
ECT signal wire
Measure signal voltage and compare to engine temperature using a
chart.
A typical hot engine reading is .5 to 1.5 volts
A cold engine reading varies greatly dependent on ambient
temperature. Any where from 2.5 to 4 .5 volts
•
Signal fixed at 5v r(tigure 2)
Check sensor ground, if sensor ground is good either the thermistor
or the connector is bad (open).
•
Signal fixed at Ov r(tigure 3)
Disconnect the sensor, if signal voltage jumps to 5v the sensor is
shorted. If signal voltage remains at Ov there is either a short to
ground or an open in the signal wire. Compare to scan data to
confirm. If scan data also shows Ov the circuit is shorted to ground. If
scan data shows 5v, there is an open in the signal wire. ,(figure 2b)
2.
ECT ground wire
Measure ground voltage
Should be less than 100 mv
3.
No signal or signal out of range
Disconnect ECT sensor and measure signal voltage
Should read near 5 volts
11
m'7 ~
Intake Air Temperature Sensors~
(IAT)
•
0
G
~
Description and operation
Used to measure incoming air temp.
• Air temp. affects air density which affects how much air will enter
a cylinder
- Cold air = more dense = more fuel
• Input is used to adjust fuel curve.
- Some manufacturers claim the fuel curve is only affected by
5°/o based on IAT input.
Located in the air cleaner box, air intake hose, part of the MAF
sensor or mounted in an intake runner.
• An intake manifold mounted IAT will read hotter temperatures
than an air cleaner mounted IAT.
Other names and abbreviations for the IAT sensor
1. MAT - manifold air temperature sensor
2. ACT - air charge temperature sensor
3. Battery temperature sensor - (Chrysler)
12
IAT Scan Tool Testing
1.
2.
3.
0
G
4.
5.
Compare ECT and IAT temp. on a cold engine
•
Should read within 5 deg. of each other
Compare ambient temp. to scan data IAT temp.
For manifold mounted IAT sensors:
Engine running, IAT should read cooler than ECT
- If IAT reads hotter than ECT, the EGR valve may be stuck
open.
- This condition may even set an IAT sensor related
trouble code
For air box mounted IAT sensors:
Engine running , IAT should read near ambient temperature.
Scan data and voltmeter wiring test are the same as the ECT.
13
Exhaust Gas Temperature Sensor
•
(EGT)
- Used to monitor EGR flow.
• For proper EGR control.
• For diagnostic purposes.
0
G
•
- As flow increases signal
voltage decreases.
- Mounted on the intake side of
the EGR valve.
Testing the EGT
- Use the same electrical
testing as other thermistors.
- Open the EGR valve with the
engine running (see Section 3
for manual solenoid activation
procedures) and watch for the
EGT signal voltage to drop.
The more the EGR valve is
opened the hotter the EGT
gets, due to hot exhaust gas
entering the intake.
The only time exhaust gas
flows through this tube is
when the EGR valve is open.
As EGR flow increases,
thermistor voltage should
decrease.
14
All Other Thermistors
•
Follow the exact same tests as you would for an ECT sensor with the
exception of what changes the thermistor temperature. For example if you
are testing an evaporator core temperature sensor for a signal voltage
change you would not just run the engine as with an ECT sensor. You would
need the AC system activated for a temperature change to take place in the
evaporator core. Think about the system you are working on .
0
G
15
(Return)
Figure 2
Scan Data Signal Fixed at 5 Volts
a.
PCM
-----------------,
I
I
I
I
I
I
5v . • ... • . • ..
'
5v
11:
I
I
I
I
I
I
I
I
I
I
I
5v
>
.
Signal return
'
0
5v
'
I
I
I
I
I
I
..
... .......
......
!
t
From Sv regwtor
>
\
I
I
-----------------,
5v
I
From Sv regulalor
0
Si!1181
!
b.
PCM
Thermistor
>
11:
open ground
'
5v
I
I
I
I
I
I
I
I
I
I
I
Signal
opons1jN!we
5v
Ov
>
\ >
.
Signal return
Ov
•
Thenn1stor
>
'
I
I
I
c.
PCM
~------------- -- -,
5v
t
...
I
I
I
I
I
I
. ......
~
• • •
:
From Sv regulator
Sv
ti:
Signal
I
I
I
I
I
I
I
I
I
I
5v
"""" thlrn1s1or
'> Thermistor
.
Signal return
Ov
>
'
I
I
'
16
(Return)
Figure 3
Scan Data Signal Fixed at 0 Volts
PCM
a.
-----------------,
Sv
t
Shofted &q1al ..we
0
PCM
Sv
-
From Sv regulator
ov
I
I
I
I
I
I
I
•
'I
•
t
Ov
d.
~----------------,
From 5v regulator
Shorted &q1al wwe
Sv
Thermistor
Signal return
11
PCM
v
t
Ov
Signal return
Sv ............
Signal
Thermistor
Shorted Lhermslllr
tI
b.
-----------------,
Ov
Thermistor
ti
G
Ov
From Sv regulator
Ov
Signal return
Signal
I
Ov
From Sv regulator
c.
-----------------,
Sv
Signal
Ov
PCM
Ov
11:
I
I
I
I
I
I
I
I
I
I
I
i
I
'
Signal
Sv
\
>
Thermistor
Shorted Lhermislor
>
Signal relurn
Ov
17
Potentiometers
0
0
Section 7
m'7~
Throttle Position Sensor (TPS)
•
Description and Operation
•
TPS input is used for the following outputs:
1.
Accel. enrichment
-
2.
A rapid opening of the TPS = computer adds
extra fuel (figure 1l
Decel. fuel cut off
0
G
Computer prevents decel. stalling by opening up
IAC passage after any increase in TPS signal
TPS
voltage (see picture to the right)
Back up for a MAP or MAF failure
-
5.
cnt
17
Idle speed control
-
4.
89
IAC
A rapid closing of the TPS = computer shuts off
injectors completely (high RPM only) (figure 1)
3.
~
Computer w ill use RPM and TPS to estimate
incoming air volume
1.78
v 0.65
2188
Some of the other outputs controlled using TPS input:
RPM
1. EGR
6. Spark Timing
2. Open/closed loop
3. AC clutch
4 . Transmission shift points
5. Clear Flood Mode
KOER while lightly snapping
throttle. Notice IAC response to
TPS changes.
2
Faulty TPS Symptoms
Hesitation on acceleration, usually just off idle
High idle speed
Low idle speed
Rolling idle speed
Stalling at stops
No start (TPS stuck at WOT during cranking)
AC compressor clutch does not engage
Transmission does not shift, electronic shift only (limp mode)
3
(Return)
Figure 1
TPS - Injection Pulse Comparison
v
-------- ...------------- ... --------------·--------------·- ----------
v
--~ ------------- ~------------- ~-------------:------------- : ----- 5
'
'
.
.
'
.
.
.'
5
- - - - - - - - ~- - - - - - - - - - - - - -:- - - - - - - - - - - - - -:- - - - - - - - - - - - - -:- - ~ - - - - - - - - - - -:- - - - - - - - - - - - - - :- - - - - - - - . - - - - - ~ - - - - - - - - - - - - - ~ - - - - - - - - - - - - - ! - - - - - - - - - - - - - ! - - - - - 4
4
. Rapid
. Acee~
..............................
....,•.
•
•
•
l
.
---~-------------~-------------:-------------~----- 2
.•
.
.
.
.
.
.
.r- ------------ .r------------- .1-- -- - -- - -- - --r.-- - --1
----- 0
'
..
.--------------r-------------r--------•
.
'
.
.
.
----:---- ------- -:-
.
.
.
..
.:--
------------- ~ ------------- ~ -------------
.
'
----.----
.•
.,• .
-------------• ------------- ..• ------------- -- -- --2
80-- -- -- - ~ -------------~-
-1
4 0-- -- -- - ...•------ --- --- .•-
·3
MAP
.
.
120-- --- --- .:;_---- -- --- --- .. _- --- --- --- ---·-' -- --- --- --- __;_--- --- --- --- -~ - --- --- --- -- -~' -- --- --- --- -- ~ --- -
0
-2
~W.J;M'l>N/;''~j\~mll\llW
•
'
~apid D~el
- - . ;. - . - - . - .. - - . - . ;. . - . - .. - .. - ... ; . - .. - .. - .. - - . ; - . - - . 3
20 0· ....... ;_ ............ ; ..... - . - .. - -..:.
'
.
· · · · · • · · · · · -:;rv
-
.
.
.
.
.
2 160- - - - - - - - -:- - - - - - - - - - - - - -:- - - - - - - - - - - - - -:- - - - - - - - - -
3
0
TPS
mV
0- - - - - - - - ~- - - - - - - - - - - - - ~ - - - - - - - - - - - - -
.
-
.
~
.•
-t"--~ -~-:. _-~ ~- ~ -------_._..,~--·_-_._--·_-_._-_-_._-_,~,.._·_-_-_._-_._-_-_·_-_._-_·.':"--_·_-_._-_-_._-_._-_._-~.,;·_-_._-_-__
-i--------------i- -----------
.
-4 0--------~-------------~--------------:----------- ---.----'
------1
'
3
.
'
'
Inje·. c tor·!.P:w:···!·····
.
.
'
-------~-------------;------------- ; ------4
'
·4
-750
-500
•' •
-250
Double pulse from injector
enrichment
------···-·····-·· --~-- ----------~ -----~-----~~-----·
------~---·-········ · --------~---- · ~-- ··5
750
1000
1250
1500
0
-- AceeI
250
500
-
No injector pulse - Decel fuel cutoff
4
m'7 ~
~
Throttle Position Sensor (TPS)
•
•
Description and Operation (continued)
Most are three wire sensors (Figure 2)
1.
2.
5 volt reference is constant (always near 5 volts and never varies) and may be
shared with other potentiometers, pressure sensors, and hall effects.
Signal varies from low voltage at idle (under 1 volt) to high voltage at WOT
(usually over 4 volts). Signal voltage follows throttle movement and should not
glitch or drop out.
3.
0
•
G
Ground circuit should be constant (less than 100 mv) and may be shared with
other inputs
Some are four wire sensors
1.
•
•
•
A Toyota 4-wire TPS contains a potentiometer and an idle contact switch.
(Figure 4!
2. A Ford 4-wire TPS contains 2 separate pot. signals, while internally sharing a
5 volt ref. and ground. (Used on electronic throttle systems) (Figure 3)
Some are not potentiometers at all and only contain two internal switches. (Figure 4)
Nissan uses a 6 wire TPS on some models. It contains an idle and WOT switch and a
potentiometer. (3 wires for the potentiometer signal and 3 wires for the switches)
With electronic throttle control systems the TPS may be an integral part of the throttle
body unit and is not serviced separately.
5
(Return~
Figure 2
Three Wire TPS
Notice there is no current limiting
resistor and the PCM is not
monitoring the reference circuit
as it would a thermistor.
PCM
5 Volt
Regulator
1--T"---i
0
G
WOT
-----
The PCM i s
" watc hing" the
voltage drop
acros s thi s fixed
re s isto r.
IDLE
-
...
5 volt Ref
...
'
''
''
''
'
Signal
Signal Return
'
'
'I'
Potentiometer
Voltage
Sensing
Circuit
11
As with a thermistor, the voltage sensing circuit does not
support current flow. Current flow through this circuit is from
the Sv ref. through the resistor to ground .
6
£Return.~
Figure 3
Ford Electronic Throttle Control TPS
..
.
..
.
..
.
• •• • •• •• •• • •• • •• • •• •• •• • •• •
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3.5
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GRYIWHT
YEUWH-r---:=:::===========- TPS Signal Wires
YEL.JWH T
PNK/ORG
5 Volt Ref
Ground
l,..J...Af./'
7
(Return~
Figure 4
___....
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.
IDLE
QAM- Polarity here determines
"--1
circuit design
__
....~ QRN..YEL
.._
-
WOT signal
'--
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'i YEl-ILU
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ldlesignal
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ELECTRONIC THROTILE
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YB.-ew ', FUH ID
Older Nissan design
THROTTLI
0
BlU...wHT
lHROTILE
POSITION SENSOR
Ford 4-wire used
on ETC systems
Conventional
potentiometer
8
TPS Scan Tool Testing
•
1.
2.
3.
0
G
4.
http://www.youtube.com/watch?v=nfnkTOlkiBs,
KOEO
Look at TPS Volts at IDLE and WOT
IDLE= under 1 volt (.3 to .9 volt typical)
WOT = 3.5 to 4.5 volts
Look at TPS 0/o at IDLE and WOT
IDLE= 0 to 10°/o (some cars must be 0°/o, see Section 20 pages 6-8)
WOT = 85 to 100°/o
Perform a TPS sweep test
must open and close the throttle slowly to see any glitches or dropouts
Limit data PIDs to speed up datastream sampling
Signal Wire Tests (TPS 0/o may show a defau lt value see ·\substituted Va/ues,i')
a)
Perform when TPS signal voltage is fixed at 0 volts
•
Unplug TPS http://www.youtube.com/watch?v=h17kYyFrExE
•
TPS volts should read 5 on some models and 0 on others (Figure 7)
If it reads 5 the signal circuit is good
If it reads 0 then jump the 5 volt reference wire to the signal wire
using a 5kohm resistor (added protection from a short to ground)
If scan data TPS volts now reads 5 then the signal circuit is good
Perform when TPS signal voltage is fixed at 5 volts
b)
•
Unplug TPS
•
Jump TPS signal wire to TPS ground wire
If scan data TPS volts now reads 0 then the signal circuit is good
*Note* DO NOT JUMP THE 5 VOLT REFERENCE WIRE TO GROUND! 9
TPS Voltmeter/Scope Testing ffi~ ~
(Potentiometer Type)
•
•
•
0
G
~
KOEO or KOER
Connect negative lead to a known good ground for all tests
http://www.youtube.com/watch?v=znw-gjLEOfk
Connect positive lead to:
1. TPS Signal Wire
http://www.youtube.com/watch?v=8KfKflmo1XgJ
• Check at IDLE and WOT and compare to spec
- Under 1 volt at IDLE (.3 to .9 volt typical)
- 3.5 to 4.5 volts at WOT
• Perform a sweep test {Figure 5)
(Figure 6l.
'
- If using a voltmeter you must perform this test slowly
• For intermittents heat and vibration are the keys to re-creating the fault
• If no signal or signal out of range
1. Check 5 volt reference and ground
2. Check for opens and shorts in the signal circuit using "Signal Circuit
Integrity Tes ti ngl'
2. 5 Volt Reference Wire
• Should read close to 5 volts
• If low or no voltage refer to "The 5 Volt Reference Circuit" for further
testing
3. TPS Ground Wire
• Should read less than 100 mv
• If voltage is too high = high resistance in the ground wire from sensor to
PCM, bad PCM ground or bad PCM
10
(Return)
Figure 5
TPS Sweep Test
0
0
_/
Known Good " Sweep Test"
A Glitch will usually
occur just off idle.
11
(Return)
Figure 6
TPS Sweep Test
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•
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4 · - ............... -:•·· .......................................................................... .
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.
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:
......................
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•
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ch~nges
.
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.
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.
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.
0 - - - - - - - - - - - - .... - - - - - - - - - - - - - - .. - - - - - - - - - - - - - - .. - - - - - - - - - - - - - - -·- - - - - - - - - - - - - - - .... - - - - - - - - - - - - - - ..' - - - - - - - - - - - - - - •r-' - - - - - - - - - - - - - - -.- - - - - -
12
{Return~
PCM
Figure 7
S Valt
Rttullkl
Sensor
Unpl ugged
Skohm
12 v
5
0
<
Yobu• $9Ming
Clrtu•
0 "'
11
0
Normal KOEO
sensor
unplugged
readings
G
Sensor
Unpl ugged
<
•Vall
R19"llM
12v
5
V.·
Skohm
PCM
5
' ~100kohm
'
Yoltave Sensing
CIR:'Ylt
0
This inte rn al r esis to r
does not affect the
TP S s ig n al vo ltage as
lo ng as t he sen sor is
p lugged 1n .
11
13
PCM
Figure 8
S Valt
Rttullkl
Sensor
Plugged in
12 v
5
.45
_,,,.
Yobu• $9Ming
Skohm
,,
Clrtu•
.01
11
0
Normal KOEO
idle position
readings
G
Sensor
Plugged in
12v
"----'
5
.45
Skohm
PCM
This intern al r esis to r
d oes n ot affect the
~1;:::00=k=o=h=m==:;---~L- TP S s ig nal vo ltage as
<E-- - - - - - - - - - - - - -+-...L--l ....~;;.":.;"'"•
lo ng as th e sen sor is
plugged in .
.....____ _ _ _____:_::·0~1---l---__J__--_L_----11 1
14
EGR valve position sensor (EVP)
• Informs the PCM of
exact EGR valve position
for feedback control and
diagnostic purposes
0
0
- This signal does not
indicate actual EGR flow ,
flow is assumed based on
position .
• Same wiring as a three
wire TPS
• Same testing as a three
wire TPS with the only
difference being in how
the EGR valve gets
opened and closed.
ABC
Pulsed
Signal
Vent Cap
Position
Sensor
EGA
Control
Solenoid
EGA
Valve ,,._
Vacuum Source
15
Pressure Sensors
0
0
Section 8
Manifold Absolute Pressure SeP$m- ~
(MAP)
•
Description and operation
1.
2.
0
G
3.
4.
5.
Main input for engine load on a speed
density system
Measu res intake manifold pressure
High pressure = low vacuum
Ind icates heavy load
PCM adds more fuel
Low pressure = high vacuum
Indicates light load
PCM adds less fuel
As eng ine load increases, vacuum
decreases
Used as a BARO sensor (measu res
atmospheric pressure) (some)
KOEO and WOT only
Higher altitude = less atmospheric
psi. = less fuel needed under ALL
conditions
Lower altitude = more atmospheric
psi. = more fuel needed under ALL
conditions
Used to monitor EGR flow (some)
Used as one of the inputs for spark
timing
Speed Density System
Air Temp
CTS
1'
Throttle
Opening (TPS)
p
_.,I
Volumetric
Efficiency
Engine Speed
GM EGR Flow Test
RPM
MAP
I
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--·····-- , . .Open
EGR ........,,,
Cl,....
os-ed,_..,,
Closed
Less
Time In Seconds
2
m'7 ~
Manifold Absolute Pressure Sensor
(MAP)
•
•
0
G
•
~
Description and operation (continued)
Attached to the intake manifold by a hose or
directly mounted
• Hose condition is critical
- A broken, kinked, or clogged
hose causes the MAP to read
the wrong pressure, so engine
load and BARO calculations
will be wrong
Signal output may be analog or digital
-
Manifold pressure changes cause MAP
signal changes
• Low psi (high vacuum)= low
voltage or frequency
• High psi (low vacuum) = high
voltage or frequency
3
Is the MAP more important than the TPS?
c:i ~?110 mv
Ott
..=.J
x-- 13S3µ tJ,v-3 t 68µt:J.xv - 454 I µis
V
-----·· r··-----------1·----------·-1··----------- - • - - - - • - ~I - • - --: - - - - - - - - - ;Q.I - -- - - - - - • - - - - - - -- - • - - - - • - - - - - - - - - - - - - - - - - - - - - - ~ . ....
I
'
I
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;
t
i
2.0
I
'
I
vo ltage 1.6 VOe
3.0
....... ~ ............·;.............;..................... +... ~- .........+.~- ............ ~- ........ '-~~---------' .....·
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1.0
l ?O
o. .,;
U U · •••••• ~ ••••••••••• •
u .u
<4U· •••••• ~' • • • • •
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0
..=.J I oc 3
u ""
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t·...........·t·............ ....... ·
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~ -..
r···········.,········
J
- r.s
-80
....
•
....
-·
:
-12
;
/\ = MAr
H.l
TPS voltage .5 voe 1n
bot h captu res
...........
__
.~
Injector P.W. at 1100
RPM in gear = 4 .54 m .s .
·---~- --
:
•
:--------------~------ -~ . u
•
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.
:
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·
·
~
mo
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~Ing ... .l~-'-~I.:' rnv
.
.
20
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l.:'jl(;
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q
v
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I
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·
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........ ; . ............ ; . ............ i . . . . .... J•. •• ; .•• • .l ...... . ~·-··· · · · ····- ~· - ····· · ·
I
Average MAP
vo ltage 1.1 voe
!
!
•
I
:
I
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-----· t · ------------; ------------- ~- ------- ·i-· -- ~ ---- "j" --- -- - ~- -- --- -- --- -- ~- - --- --- - '--~----~----~ - --- ·
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u . ...
uu- - - - - -
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4 0 - --- ___
- •.s
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"><=- 1 :'1!'>:'1 11.:t, i"• = l SSC111.:t,"><•.. = ?~OF011o:t
1 .5
- 1 . ll
~,,._._
1------~------,-,
------''c;
111 nn ...... ,.,., ;,·, '.)•~ ~···1
A = Trs
.....v
.....,
- 0 . !'i
-·
•
0
~
epeat ...
? .n
-~
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..--·-·-+ --···-- ---~----~ ··-· ~-·-·--.
.
~--------------~------ -1 . G
O· • • • • • • r · · · · · · · · · · · ·: · · · · · · · · · · · · ·
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t ___ --------- .l .. --------- -- ~ --------_____ j __ - --- ---1- -n .._--'· --------'"'-':'-·'•
!
--. ----- I
I
- --- -- ·
·12
-0
-4
A = MAP
!waitin g tor AUC
Trivv-.:• l no..:1·-.:~~ - I
, .~ -
----- - -~,_--- -- - ---- --- ~,_- ---- -- - ---- - ~'. - -- --- -- - - ---i,_--------- ---- -~. --- - --- 1 .0
_____,._..__......._....-_._.....,.,.---------~--··-;· --.-.-·-- - - - - - -- - - - - - - - - - - - - -•- - - - - - - - - - - -
Injector P.W. at 3000
RPM in park= 2 .95 m.s.
0
_J
l$011V
:-
t:tuuu r-prn, In pl'ltkJ
- 1 . !i
-------------~------ - ~ . u
..
·------··------ .-·~-----
a = 'l "PS c = lnJeCt()I" Curt~n•
lo.:•• C - I ( n;l:J;,,!J - I ls1
' .l
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-1 c
.
~
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20
2 .5
mo
4
Analog MAP Circuit
Intake manifold pressure
~
j
Silicon
Diaphragm ....
-l
PCM
.
~
5 Volt
Regulat or
..............
•
Absolute
zero
0
1 '> .,
J
-
-
Filtering
circuit
-
5 Volt Ref
......
Signal
-
Ground
....
'"'I
G
11
•
3 wire pressure sensor
5 volt reference
Signal
Ground (signal return)
I
Voltage
Sensing
Circuit
11
Range is O to 5 volts
NA e ngine
Idle = .5 - 1.5 (most)
KOEO or WOT= 4.0 to 4.5+ volts at sea level, most (as
altitude increases voltage decreases)
Example: 2007 Honda Civic SI is around 2 .8 volts KOEO or
WOT so make sure you look up the specs!
Turbo engine
Idle = .5 to 1.5
KOEO = 2.5 (changes with altitude)
WOT= 4.5+ (depends on how much boost psi)
5
Ford Digital MAP
Sensed
pressure
Flexible ceramic
diaphragm
Moveable capacitor
plate, mounted to
diaphragm
PCM
~--
5 Volt Ref
y
0
0
Vent
5 Volt
Regulator
Signal
F~ capaotor
plate (negative)
on ceramic bed
I
L - + - - - +----'---- - - . . _ _ _ _---l I
Rigid
ceramic bed
Voltage
Sensing
Circuit
Sealed
difference pressure
Range is 90 to 160hz
Idle= 92-112hz
KOEO or WOT= 160hz@
sea level {as altitude
increases frequency
decreases)
Same wiring as an analog
MAP the only difference is in
the signal circuit.
If the signal is measured with a
voltmeter, you will read around 2.5
volts regardless of frequency
changes. You must use a frequency
meter or scope to measure a digital
input
6
MAP Problems
•
MAP OTC
Is the MAP faulty causing the engine to run poorly, or is the engine
running poorly causing a false MAP code? (due to low manifold vacuum)
1.
Check manifold vacuum and compare to MAP Signal on scan data.
2.
Check vacuum hose to MAP for cracks and breaks.
Visual inspection
•
MAP Testing with or without OTC
Wiring tests
•
0
•
G
•
5 volt ref. and ground circuits are tested the same as a potentiometer. Refer
to Potentiometers and The 5 voTt reTe'rence circuit for details.
Signal circuit testing for an analog MAP is the same as a potentiometer with
the exception of what causes MAP signal voltage to change. Refer to Signal
Circuit Integrity Testing ;section for complete details.
Signal circuit testing for a digital MAP requires different testing methods. You
must use a frequency meter or scope. Refer to ,S witch Inputs section for pullup and pull-down circuit testing of a frequency generating device.
Calibration test
•
May need to be performed on a system that uses a MAP for EGR flow
monitoring. A slightly out of range MAP can cause false EGR flow codes.
This test involves using a hand vacuum pump KOEO while monitoring signal
voltage changes.
7
Analog MAP Glitch
..( COH
• DC• Of •
:J~oc '.lfof• o'l"oH
- -"ii.Poc,;;·il-O""i"
f·
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.
.
...'
....
0 OH
...
·~······ ·······~-········ ........ ········-··-····-········
·······- ...... .
: :·: : : r::. :.. : : ·' :~1~~rt11~1~~1 ~.~~~ . ·: :·: :: : : :.
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" ..... r· . : : i :
.
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ll~.11n1~v
.
11
.
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.
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. :
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·l···
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.
.
.... :'
:
:
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.
Bad MAP Sehsor
...
....
.
.
.
·4 ......... .............. ,:.............. ·! ..............·: .............. .............. .............................................................,
...
...
...
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.
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.... ,, ....
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..... .....
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.
.
.,
•
Good MAP Sens6r
.3............... .'...............................i···············~··············~···············l············ ..·!·······························:·.. ·············
.
.
~·
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02
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I.= MAP Stnsnr, Sn11p lhrottletest M.1POTf. 32
.
'
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....
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.
. ..... .... .... .: .... .... .... -··· ..... ..... ..... ,
.......... ···········~··········· ····:···············:··········· ····~· ·············:············ ...................................................:
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!···············~
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.:
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..
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v
S···············"."······························:···············:··············:-··············: .. ·············:······························:-···············
•
.....
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IA
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J.. =W.PKOEO Sntp Tltt¢t llntr.-11 ioo4
8
Ford DPFE Sensor
•
Description and operation
•
DPFE = Delta Pressure Feedback EGR
sensor
EVRSolenoid
Input used to monitor EGR flow
Sensor measures the difference in
pressure between the two sample
ports
0
1.
With EGR valve c losed there is no
difference in pressure
DPFE
Sensor
Exhaust Manifold
Sensor voltage signa l is low
0
•
2.
Us ually under 1 volt (. 5-1 .0v)
As EGR valve opens the upper chamber
pressu re drops .
Sensor voltage signal increases in
proportion to EGR flow
3.
With EGR valve fu lly open there is a
large difference in pressure
Sensor voltage signal is high
•
Us ually ove r 4 volts
9
Ford EGR Flow Test
W!int Cap
CD Solenoid
I,.....-......::::::-o(%1evR
KOER , connect voltmeter to DPFE
signal wire or monitor scan data PIO.
Should be around .5 to 1v at idle with no
DPFE ....r-'111
EGR flow.
Sensor
1. Jump EVR control wire to ground
L!;=:Exhaust Manifold
w ith a test light to energ ize the
solenoid (may need to use a
jumper wire, BE CAREFUL!).
2.
Engine should stall or almost stall
and DPFE voltage should increase.
3. Increase RPM to 1500 to prevent
stall and re-do test. DPFE voltage
should increase to over 4 volts and
the engine should get very rough.
4. If eng ine gets rough and/or stalls
and DPFE voltage doesn't change
= DPFE problem
5.
If engine does not get rough =
there is a flow problem .
Most common EGR flow
http ://www.youtube.com/watch ?v= pH kj RwD-Xw
problem is from a restricted
intake passage
~ttp://www.youtube.com/watch?v=znw-gjLEOfk
10
•
0
G
The 5 Volt Reference Circuit
0
G
Section 9
m'7 ~
The 5 volt reference
c ircuit
0
G
• Grounds may be
shared between any
input
• Signal w ires are never
shared between
sensors
• The 5v reference can
be shared (externally
from the PCM) with
pots , psi sensors , and
ha ll effects but never
with thermistors
• A shorted pot. , psi
sensor, hall effect may
pu ll down the entire 5v
ref. circu it includ ing all
of the internal circuits
that use this same
reference voltage
• A shorted therm istor
will not pull-down the
entire ref. circuit due to
the interna l resistor in
the PCM for thermistor
circu its
PCM
-
I
I
t 2 volt supp
I
Swit c h In put
ig n al w ir
ECT
ignal wir
IAT
- volt referenc
l -- - - - ' - - - - - -1'-- - sii gnal Retu m
.
.
S ignal wir
Signal W ire
~
SVott
R$gula tor
I
Vvv
I
I
I
Cutre:f1t limiUng re~or
I
v v v
Cutre0t limit.1nQ reSistor
I
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1 -~ng :
"'<""
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y ~
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.
.
Vvv
_
Current limiting re sistor
I
I
I
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y -.... 1
I
-
I
I
I
_,...,. I
I
I -~
- ··
I
MAP
<:•- - --1'- - - - - - S i gnal Wire
VAF<:•>----------~ Sig na l w ir
I
I
I
I
I
I
I
Hall effect , - - - - - - - -S i g nal Wire
1
~
I I'
5 volt reference
Signal Retu rn
-,_,
I
J~ I
CN"ClM
I
I
tMC...t
I
I
. . .
I
I
I
I
I
I
Cu.rran t limiti:l'lg resistor
VVv
..... ,
·-I
-~ ·
1n·tegreted
C l:rcu l1
r-
I "''eg"'""'
IC ircuit
I
2
Description and Operation
•
•
•
0
G
The PCM uses a 5 volt regulator for multiple purposes (communication and
sensor inputs to name a few)
If the 5 volt reference circuit gets shorted to ground the engine will NOT
start (no injector pulse, no communication with scanner, possibly no MIL,
no flash codes, possibly no spark.
KOEO check for 5 volt ref. at the TPS or MAP
- No 5 volt ref
• shorted sensor (any one of them that share this reference voltage
except thermistors and switch inputs)
• Short to ground in the wiring
• An open in the wiring
• PCM not sending out the 5 volt reference
- Bad PCM
- No power or bad ground for the PCM
3
Testing the Sv Reference Circuit
•
•
0
G
•
•
You must have a good wiring diagram and identify what sensors share this
reference. All potentiometers, pressure sensors and some hall effects
(cam, crank, vehicle speed sensors) must be isolated to find the short.
Thermistors can be left plugged in and will never cause this condition due
to internal design differences.
While measuring reference voltage with the key on, (usually at the TPS or
MAP because of easy access) start unplugging the sensors one at a time.
Find the sensor that causes the reference voltage to return to 5v when you
unplug it.
If you still have no 5v ref. with the sensors all unplugged, then you must
disconnect the PCM and measure for a short to ground on the reference
circuit. (sensors still unplugged)
No short to ground then you have a PCM problem. Make sure you check all
PCM powers and grounds before replacing the PCM .
- Part 1 http://www.youtube.com/watch?v=a-d6-jrGidA
-
Part 2 http://www.youtube.com/watch?v=jlwNcgtv9zO
Part 3 http://www.youtube.com/watch?v=dCZdv-FYwxw
'
4
Wiring Identification
Practice using the information on page 3 to determine signal wires,
ground wires and reference wires in this diagram.
COOLANT
TEMP SE NS
- BLK- LT BL U
TAN-BLK
""'
AIR TEMP
SENS
-
BLl<-LT BlU
A
' - TAN - Bl K
B
'-
I
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::> c
cc
'
~
~ Ill
0
MAP
SENS
HEATED
02
SENSOR
I A I B ICI
!211131
I I I I
·1111 1
3 ...
~
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CD CD
0
..._, >
t_, ~
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....
_, _, :r
CD CD 3::
CD
!:;
I
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~ Q
I
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::> 0w
~
VEHICLE
SPEED
SENSOR
CRANK
POSITI ON
SENS
::;) ::;)
I A 18 1
8
.....
8lK- LT BlU
CAMSHAFT
POSITION
SENSOR
THROTTLE
POSITION
SENS
CD w
!:i
...... VlO-WlH
c OKGRN-REO
......
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CD
ccI
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g
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0
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cc
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Ill
CD
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er: a! er:
0
9
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Ill
z _,
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Ill 0 "'
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~
Ill !i :.:
c
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-
mm
"1
G
, SlK·l T BLU
TCU PIN 03 ,
-,
-'
MAP SENS
.....
2
COOLANT TEMP SENS .....
BATTERY 3
SENS GROUND
'SIG GROUND 5
.....
SENS 6V SUPPLY
~
8VSUPPLY
J.
•-
/
'
Kl OK GN· RD
K2 TAN•BLK
A14 RED
K4 Bll<·LT BLU
Z11 BLK· WMT
1(6 V10-WHT
K7 ORG
..... A21 OK BLV
IGN START/ RUN 9
KI OOK BLU- WHT (OR V10)
PWR STEERI NG SENS .....
10
7.12 BLK-TAN
/
/
VlO
• IGNITION
(4.0L,
•' Fl
•SW
-
Wiring Identification
Practice using the information on page 3 to determine signal wires, ground wires
and reference wires in this diagram.
-- --- ___ _-I
...I
(ENG HARN '
NEAR
BREAKOUT
FOR
C.APACITOR)
S105
----- -----
0
G
:::>
__J
__J
<
z S2
__J
(!)
a:
f5 CD 0
~
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<,
~•
("")
:JCD CD
':::;
-fi:
(!)
~
0
"'
("")
<,
~•
-
a:: ':i
(!) (!)
a:: a:: S2
__J
0
0
~,
·.."'', ,"', ....
, '
-
CD
CD
.•
I'
' I'
~ 'V'v
CAMSHAFT
CR.ANKSHAFT
THR OTILE
POSITION SENSOR
POSITION
POSITION SENSOR
(ON RIGHT SIDE
SENSOR
(ON THROTILE
OF ENG, NEAR (ON TRAAISMISSION
BODY)
OIL FILTER)
BELLHOUSI NG)
a::
':i
(!)
a:: ::.:: S2
__J
CD
...,
__J
3
CD
- - - --
-
~
0
0
(!)
. "' ...
I'
'
"
A, A
v
y
'
A
MANIFOLD
.ABSOLUTE
POSITION SENSOR
(ON SIDEOF
THROTILE BODY)
~,
:::>
__J
__J
:s
-
CD
z
'__J
Si:
0
CD
"",• ,,...."',
-> fi:
.....
c ':i
CD
(!)
•
:::>
__J
(ENGHARN '
NEAR
BREAKOUT
0
FOR FUEL
w
:::>
__J
__J
a:: :::>
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CD INJ 5)
CD
::.::
z
w
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I
•
--
(ENG HARN,
NEAR BREAKOUT ~ RIGHT
REAR OF ENG
COMPT)
-
w
CD
S112
S107
0
(!)
S2
__J a:
--·
-e
:::>
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CD
w ':::;
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• I'
f5
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•
.
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A , J\ '\ A
y
., y
ENGINE OIL
PRESSURE
SENSOR
(RIGHT REAR
OF ENG BLOCK)
·'
.
v " ''
CD
0
':::;
S2
__J
a::
S2
__J
CD
CD
~
w
...
"',
·'
.
v " '"
ENGINE COOLANT
INTAKE.AIR
TEMPERATURE
TEMPERATURE
SENSOR
SENSOR
(ON THERMOSTAT
(IN INT.AKE
HOUSING)
MAAllFOLD PLENUM)
6
0
G
Signal Circuit Integrity
Testing
Section 10
Purpose
1.
2.
3.
To quickly and accurately verify sensor wiring for opens and shorts
without using an ohmmeter.
To bypass an engineer written "flow chart" that was never designed for
speed.
To prevent the need to access the computer and unplug it to perform
wiring tests.
0
G
2
Using DTCs
This method is used primarily when data stream is not available
•
0
G
"Circuit high" trouble code
1. Disconnect the suspected faulty sensor.
2. Jump the sensor signal to the sensor ground wire and re-read
codes. If you now have a "circuit low" code then the wiring is good
and there is most likely a sensor problem.
•
"Circuit low" trouble code
1. Disconnect the suspected faulty sensor.
2. Jump the 5 volt ref. wire to the signal wire using a 5kohm resistor
and reread codes. If you now have a "circuit high" code then the
wiring is good and there is most likely a sensor problem.
- On some systems it is normal to read high signal voltage with
the sensor unplugged. (see pg. 5)
NOTE: The engine may need to be cranked or started to set DTCs on some
input sensors.
3
Using Scan Data
•
Potentiometers, Pressure Sensors
1.
Disconnect the sensor and check sensor PIO on data stream.
2.
Jump the 5 volt ref. to the signal wire using a 5kohm resistor. (this
step is not needed on some systems, see pg.5)
•
Look for sensor PIO to change to near 5 volts.
3.
Jump the sensor ground to the signal wire.
•
Look for sensor PIO to drop to near 0 volts.
NOTE : The engine may need to be started or at least attempted
to start for scan data sensor PIO to update on some input
sensors.
•
Thermistors
1.
Disconnect the sensor and check sensor PIO on data stream
•
Sensor PIO should read near 5 volts.
2.
Jump sensor ground to the signal wire.
•
Look for sensor PIO to drop to near 0 volts.
0
G
4
PCM
S Valt
Rttullkl
Sensor
Unplu gged
Skohm
12 v
5
0
<
Yobu• $9Ming
Clrtu•
0
ft..
11
0
Normal KOEO
sensor
unplugged
readings
G
Sensor
Unplu gged
<
•Vall
R19"llM
12v
5
V'
Skohm
PCM
5
100ko hm
~
'
Yoltave Sensing
CIR:'Ylt
0
This inte rn al r esis to r
d oes not affect the
s ig na l vo ltage as lo ng
as t hese nsor is
plugged in .
11
5
Knock Sensor Example
PCM
5v-
Signal voltage on this
design should be
1.5VDC with the
sensor plugged in and
5 vo lts unplugged
{this will be vehicle
specific)
Knock
sensor
0
G
Internal to the KS is a "bleed" resistor tha t will pull the 5v
reference down a specified amount. The PCM "watches" the
signal circuit for changes in reference voltage that would
indicate an open or shorted condition.
Knock sensor with a 5 volt bias line.
Use this picture with the knock sensor example on page 7.
There is no need to use an ohmmeter to find opens and shorts
is a circuit that uses a bias or reference voltage.
6
Knock Sensor Example
Knock Sensor Scan Data Testing With A Current OTC P0327
Is the knock sensor bad? yes
Is there an open in the signal wire? no
Is the computer bad? No
Understanding circuit design was the key!
0
G
KS unplugged. KOEO with
signal wire jumped to ground.
Signal voltage dropped to
under .1
KS plugged in. KOEO
and KOER voltage
rernained @ 4 .86. Spec
is 1.5
''
4.86
:f
KS Sensor
.II
0.18
v
0.08
7
Substituted Values
0
0
Section 11
Purpose
•
•
0
G
The PCM may substitute scan data PIOs with default values based off of
other inputs. This is also known as "limp home mode". (signal circuit integrity
testing in section 10 may be misleading do to this condition)
In general only the value of the input is substituted and not the voltage. This
will only occur with a "hard" fault (problem happening right now).
Example:
1. Hard TPS OTC in memory.
Scanner TPS voltage = 0 volts regardless of throttle position .
Scanner TPS 0/o = varies from 0 to 1OOo/o as throttle is opened and
closed
*Notice the 0/o is substituted and not the voltage
2. Hard MAF OTC in memory.
Scanner MAF frequency = Ohz regardless of amount of intake air/rpm
Scanner MAF grams/sec= increases and decreases with airflow and
rpm changes
*Notice the grams/sec is substituted and not the frequency
3. Hard ECT OTC in memory.
Scanner ECT voltage is fixed near 5 volts
Scanner ECT deg . F = 150 deg .
*Notice the deg. F =substituted
NOTE: 08011 data will never show substituted values. ,S ee page §
2
Example of a rare voltage substiiffitibn
Scan data TPS volts doesn't match
~~~~~ and never changed
0
KOEO while opening
KOEO idle position
G
0
Signal voltage
measured at TPS
"Hard DTC" in memory for TPS. Sensor tests good but scan data doesn't respond to any TPS
voltage change.
Is there a signal wire or PCM problem?
What test do we oerform next?
3
After cycling ignition off then baQ2Jk~n ~
Notice the scanner signal now matches actual signal voltage in both pictures.
RPM----At'4T' D F •
0
Pr1nt Hold
G
.l
KOEO idle position~
•..
-
"
KOEO while disconnAl!t'
sensor
J
0 .7 6 ~;t-
.96
I
After checking signal wire voltage at the ECM and all ECM powers and grounds
the scanner now reads normal and the OTC does not reset. The picture to the
right is an attempt to recreate a TPS OTC to watch the ECM's response.
4
m'7 ~
~
Immediately after disconnecting sensor
I
RPM _____ 1 02CU -C
LRNT a~ _ _ _ _ _ 156
_________ 1.25
T-BODY TEMP(U _3.11
•
Look at the response
•
The ECM has recognized an open
circuit in the TPS
•
Scan data shows the default
(substituted) value of the TPS
circuit.
This engine needed a new TPS.
The wiring and ECM were fine.
If you were not aware of this
condition you may have
condemned a perfectly good
PCM.
TPS~
0
•
G
•
5
(Return)
Scan Data with ECT unplugged
OEM
Global OBDll
~11 ~~CL£AA l!J C\z~ e. J
QJ~~ ~11 ®CLE•Al! l C\z~ e. I
-
0
G
Qj~fl
•
0
104
0.60
0.5
0
0
12.2
0.0
TPS(V)
~NF SE-B1V
NF Al.PHA-B1rkJ
VEHSPEED(MPH)
BATTM
BIFUEL (MSEC)
200111SS.VUl.11M UL 1.4Ill (KA2.q)
•
ID:$
ENGINESPEED(1/min)
ABSOLUTETHROTTLEPOSITION(%)
FUEL SYSTEM1
FUEL SYSTEM2
INTAKEAIR TEMPERATURE('~
•
AIR FLOW RATE(g/s)
10
0
3.5
OPEN LOOP
,112Ql11f j f~ J • I
Substituted value
j02123111 J t?ltp J
Actual value
The point with this is you just need to be careful. The global 08011
mod e will never substitute a va lue, but the OEM may.
6
Airflow Sensors
0
0
Section 12
Vane Airflow Meter
(VAF)
•
•
5 or 7 wire sensor located in front of
the throttle body
All incoming air must pass thru the
sensor
•
0
Contains an air measuring plate that
is pivoted by incomi ng air flow
-
0
-
-
•
•
Vacuum and air intake tube lea ks
cause major problems on these
systems
No air flow = plate closes completely
WOT = plate is fully open
Attached to the plate is the pointer of
a potentiometer
Position of the air plate and pointer
indicate to the PCM exact incoming
air flow
PCM uses this input to determine
engine load , injector pulse and ign.
Timing
Contains an intake air temp. sensor
May also contain a fuel pump cut off
switch (7 wire only)
4.Z
J.6
J.D
2.4
1.8
1.2
.,.,.~-
~~
0.6
2
VAF testing
•
0
5 pin
- Check VAF potentiometer signal
• Signal voltage should follow RPM w ith no glitches or dropouts (compare voltage read ings
with specs)
- The air measuring plate can stick or bind causing incorrect signal voltage to the
PCM.
» To test: KOEO measure signal voltage while manually opening and closing
the air measuring plate. Signal voltage should follow plate movement.
• If signal is out of range or no signal appears (see "Potentiometers" for complete circu it
testing)
- KOEO or KOER
- Check the reference w ire (should be 5 volts) and the ground wire (less tha n 100
mv).
- Check the signal wire for opens and shorts. (refer to Signal Circuit lntegrit~
Testing)
G
•
- If above checks are good, replace the sensor
- Check VAF intake air temp signal
• See "1Thermistors1' for complete circuit testing
7 pin (Toyota)
- Testing the VAF pot. signal and IAT signals is exactly the same as the 5 wire type
- The extra 2 wires are part of a fuel pump cut off switch which shuts down the fuel pump if the
engine stalls.
• Air plate fully closed = FP switch opens
• Air plate in any other position but closed (any RPM above 250) = FP
switch stays closed
• With engine running , both FP switch wires should read 0 volts. KOEO one wire should
read 12 volts and the other should read 0 volts.
3
Early Model Toyota VAF
FP cut-off
switch
AIRFLOW MEtEA
-• -
-
•
'
I I
- -- l - - ~
I
Ill
0
G
0
a::
a:I
=>
m
I
I
I z I I t I 14'1 l• l
.
'
,>
>
'
~
.J
11A
EFtFUN
'
I I
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I3 I
w
w
EFI MA.JN R.EU.Y
-
fl
171 l sJ l•I l'I llltl
0
REI A.Y aox "2 (PARTIAIJ
CIRCUIT OPENlllQ "ELAY
:cs a ·!
~
·~~~
ii~i
1
t
IAT
Sensor
Signal ground
(shared)
' '
VAF
Signal
t
Sv
Ref.
Hot in
run
t
FP
terminal
on DLC
, ..,. #!PIN le
_,,_....., (NIN FUH)
I\
Hot in
crank
position
only
4
m'7 ~
~
Mass Airflow Sensor (MAF)
•
•
0
G
Description and operation
Hot wire type
Conta ins a heated resistor (hot-wire) that is
maintained at a predetermined temp. above
ambient temp.
As air flow increases the current required to
maintain hot-wire temp . also increases. This
increasing current is converted to a signal
and sent to the PCM as a measurement of
mass air flow .
• Signal can be analog or digital
As with a VAF, all incoming air must pass
th ru the sensor. Vacuum lea ks and air intake
tube problems will cause "un-metered" air to
enter the engine causing mild to severe lean
a/f ratio problems .
Unique to the hot-wire MAF is problems with
contaminates . Dirt, dust, pollen and PCV
gases cause the hot-wire to become "dirty"
which acts as an insulator covering the hotwire causing the MAF signal to be wrong
under all conditions .
• Causes lean running conditions
(symptoms noticed more when engine
is cold)
If this is a " honeycomb" type
screen, DO NOT TOUCH IT!
GM Hot-Wire MAF Sensor
Air ensing
Passage
MAF
5
Scan Data MAF Testing
•
•
•
0
G
Look at MAF signal (voltage or frequency)
Look at MAF grams/sec (th is is the signals converted value)
Ford - look at BARO HZ (lower than normal HZ = possible dirty MAF). Sea level readings
should be near 160HZ. Barometric pressure is calculated off of the MAF at WOT.
http://www.youtube.com/watch?v=h5KAHv4 7viw (Using Fuel Trim data to determ ine type of
lean condition)
1. Check at idle and WOT (redline)
2. May need to test drive for the WOT test if scan data baud rate is slow
• Pay close attention to the WOT redline values
• Look for near 150 grams/sec for most GMs and Fords (some systems will be less
than th is. http://www.youtube.com/watch?v=Hmt LNJ9Gkl (Toyota Dirty MAF)
http://www.youtube.com/watch?v=-5L5tp4NDqO (Cracked air intake tube)
• Ford, Nissan, and Toyota signal voltage should go over 4 volts
• GM frequency should increase to 8,500 HZ or more
(see pages 1Q, 12. and .Ll. for case stud ies)
3. Check 02 mv at WOT (test drive)
• 02 should read rich (800 mv +) if the MAF is clean
• 02 indicates lean then possible dirty MAF or other fuel delivery problems
4. Check fuel trim
• Generally a dirty MAF will have normal fuel trim numbers at id le and higher than
normal (positive) fuel trim numbers with higher RPMs
• On occasion a dirty MAF can over estimate air-flow at idle . The contaminants cause
an increase in surface area , which under low airflow conditions cause a greater heat
transfer. The PCM "sees" higher airflow so it provides more fuel. This causes the
fuel trim at idle to be negative.
5. Can try the unplug it test if the signal is out of range . If the eng ine runs good with MAF
unplugged = suspect faulty MAF
• The above test is NOT always accurate. Some systems do not provide good back6
up strateg ies for MAF failures . (N issan , Toyota, Subaru)
Scope Testing MAF Sensor~~~
•
•
•
0
G
•
~
Digital Type
To determine if the MAF sensor is dirty you must measu re peak frequency .
Peak frequency is best measured using a graphing multimeter (Snap-on Vantage,
Picoscope 4000 series) which allows the digital signal to be converted to analog for easier
measurements. (see page 11)
1.
Measu re signal frequency at idle and WOT redline (see examples)
Look for over 8500 HZ at WOT (newer GMs)
If frequency is low then remove sensor and inspect hot wire for contaminants
(see picture on pg. 14)
Clean with brake cleaner and a soft paint brush (hot-wire type only) - BE
CAREFUL! Do not clean any other type of MAF sensor with brake or carb .
cleaner!
http://www.youtube .com/watch?v=h5KAHv47viw (Digital MAF test with
Picoscope)
If signal is out of range or no signal appears
1.
Measu re MAF power feed KOEO or KOER
Should be near 12v
2.
Measure MAF ground KOEO or KOER
Should be less than 100 mv
3.
GM only, disconnect the MAF sensor and measure signal voltage harness side w ith
the KOEO
Should read 5 volts
The PCM sends 5 volts down the signal wire to the sensor and the sensor
pulls it to ground to create "square wave" signal. (see switch inputs for more
details)
If no voltage you have a PCM or a signal wire problem , NOT a MAF sensor
problem.
http://www .youtube .com/watch ?v=p2QLxxstRn8
7
http://www.youtube .com/watch?v=E8sBg7kMbOw
Scope Testing MAF Sensom"
•
•
•
0
G
8
Analog Type
To determine if the MAF sensor is dirty you must measu re peak voltage
1.
Measu re signal voltage at idle and WOT redline (see examples on pg. 1...§. and 1§.)
Look for over 4 volts at WOT (Ford, Nissan, Toyota)
If voltage is low then remove sensor and inspect hot wire for contam inants (see
picture on pg . 14)
Clea n with bra ke cleaner and a soft paint brush - BE CAREFU L! Do not clean
any other type of MAF sensor with bra ke or carb. cleaner!
http://www.youtube.com/watch?v=H mt LNJ9Gk I
If signal is out of range or no signal appea rs
1.
Measu re MAF power feed KOEO or KO ER
Should be near 12v
2.
Measure MAF grou nd KOEO or KOER
May be more tha n one grou nd
Ford uses two grounds . It has an MAF ground and a PCM ground . The PCM
gets its ground th rough the MAF sensor . This is important to know when
performing signal circu it integrity testing because the PCM w ill not respond
to any test with the MAF sensor unpl ugged .
All grounds should be less than 100 mv
Some MAF sensors conta in an internal intake air temperature sensor identified by the
number of w ires .
1.
Ford 4 wire = MAF signal , MAF ground , PCM ground, MAF power feed .
2.
Ford 5 or 6 wire= MAF signal , MAF ground, PCM ground , MAF power feed, IAT
signal , and IAT signal return (which may be sha red w ith another ground wh ich would
eliminate one wire)
3.
Testing this IAT sensor is no different than any other therm istor
8
m
<=>
'V """"'
MAF signal low with good MAF senSor
•
o.
Vehicle exhibits similar symptoms as a dirty MAF sensor however the
sensor is clean. (Ford BARO HZ will also be lower than normal)
1.
0
-~
2.
G
..
Plugged exhaust
•
If the engine cannot "exhale" it cannot "inhale" so intake air volume will
be low under all conditions.
•
A quick test to identify this condition is test drive at WOT and watch
02mv
02mv fixed rich (over 800mv) at WOT suspect plugged exhaust
02mv fixed lean (under 1OOmv) at WOT suspect low fuel pressure
Intake restriction
This condition will show a weak/low MAF signal no matter how you test
•
it.
,.~
(
.,-
MAF OTC with good MAF sensor
Usually sets a "range/performance" code and
may be caused by the following:
1.
TPS problem
2.
Vacuum or air intake leak
3.
Oil cap or dipstick problems
4.
PCV system leaks
5.
Dirty/plugged air cleaner
9
(Return)
Digital MAF Sensor Case Study
97 B uick LeSabre
3800 series II
3 wire sensor
Scan Data
Clean MAF
Dirty MAF
0
0
•
1997 BUICK
•
3.8L V6 BUICK SFI
AJC
A/T
0
100
•
RPM_5699 TPS(V)_ 4.22 TPS( /o)
•
•
OPEN/CLSD LOOP_OPEN
17 02 B1-S2(mV)
02 B1-51 (mV)
•
ST TRIM(o/o}
•
MAF(gm/Sec)
•
AJC
A/T
•
1997 BUICK
•
3.8L V6 BUICK SFI
•
RPM_5530 TPS(V)_ 4.22 TPS( 0/o)
•
100
35
•
OPEN/CLSD LOOP_OPEN
946 02 B1-S2(mV)
02 81-51 (mV)
16
•
ST TRIM(%}
84.1 MAF(Hz)
7473
•
MAF(gm/Sec)
143.0 MAF(Hz)
8886
MAP(V}
4.43 MAP("Hg}
27.8
•
MAP(V}
4.49 MAP("Hg}
28.1
•
BARO(V)
4.64 BARO("Hg)
29.0
•
BARO(V)
4.64 BARO("Hg)
29.0
•
COOLANT(°F)
151 INTAKE AIR(°F)
63
•
COOLANT(°F)
203 INTAKE AIR(°F)
77
•
IAC POSITION
120 DESIRED IDLE
775
•
IAC POSITION
95 DESIRED IDLE
600
•
INJ PW(mS)
11.4 FT CELL
4
•
INJ PW(mS)
0 LT TRIM(0/o}
0 LT TRIM( 0/o}
942
16
4
19.6 FT CELL
10
(Return)
Digital MAF Sensor Case Study (cont.)
97 B uick L..:::e-=S-=a""b""'re::;.._ _ _ _~-------I
3800 seri es II
I
I
10k
3 wire sensor
I
I
I
Scope Captures
I
I
I
10k
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
•
WOT snap w ith clean
WOT snap with dirty
0
MAF
MAF
0
•
0
6.72k
6.84kHz
G
8.32k
8.52kHz
I
I
I
I
10k
I
Digital Waveform
at idle
Graphed digital waveform at
idle both before and after
cleaning no change/
..
.:
...
..
..
=
I
I
•
...
.
I
I
I
5.01V
5.01VDC
-1
2 .40k
..•
..
..
..•
...
.
0
2 .41 k Hz
11
Before
cleaning MAF
sensor
lni PWM Avg Bank 1
lni PWM Avg Bank 2
14.47
I
I
I
=ec
4829
rpm
0
868
ensOf v
(Return)
22
m
894
22
ensor v
7665
2000 Chevy
S-10 4.3L
e Study
requency
z
21 15
l l l 25
3 .9
- . .
lni PWM Avg Bank 1
msec
488 4
fter cleaning
MAF senor
rpm
634
981
56
994
87
8572
requency
z
2429
154 23
s
5 .33
12
I
I
I
•••
'
•
Before
cleaning MAF
sensor
•
~ ngine Speea
n
IRl! ,,; ~
en•or l
5460 rpm
~
•••
•
•
.ri
898
m\I
J:)
ICMl
•
~
•
•
•
(Return}
•
t=::l.9
MAI" frequency
•••
•
•
•
Mat t All flow
1W.t>ll
28091
....
103 69
al•
. . . . ..
0
CD
After cleaning
MAF senor
-..
WOT
43
•
Redline RPM
•
•
•
••
I~ ng1n e Speed
"
5506
\
rpm
••
••
•
t--.
~ensor 1 Volt
••
••
18. 16
n1 Pulse Width
••
••
•
I
Frequency
;;;
8783.7
1!'iO:
8783.7
Hz
•
11" Semorv
.. . . ..
4.16
..
-
2821.8
144 93
g/s
•••
•
~
msec 2.84
•
144.93
17
19.68
••
•
Mass Alf
747
916
mV
898
I
6 45
416
4.16
~ enscwv
1 4 31
Hz
•••
••
1r
~
7859 .9
•••
•
•
22
msec 4 12
10.74
ntPul• e...?ldih
745
6.58
4.16
v
0.43
.
13
(Return>
Clean I Dirty Hot Wire
14
m'7 ~
~
Analog MAF Sensor Scope Testing
(Return)
5
1:::::::::-1.::tru·
Known Good 94 mustang 5.0
ns
... 0.12 v
4.04 v ;:~~r:~s:
Known Good 96 altima 2.4
1. 49 Hz
Initial peak
4
Initial pe~
3
3
I~
z
.
1
i-.,.......,..,,.~,___,.,.._,...,.,
.
1
,,._1,_, , ,,_......... . . ., __ .......... ~, ..... .
.
0
G
z
0
Initial peak was s lightly low, however there
where no drivability problems on this engine
0
<'.......
11
r~-·'
I n .. •••-""•-•-1 ~.... t .. !£......_
I t\tuti•
•
The goa l in these captures is to see peak MAF voltage . Performed during a rapid WOT
snap to red line.
•
Record both initia l peak voltage and red line peak voltage.
•
To see peak MAF voltage
1.
KOER with a hot engine at idle
2.
Snap to WOT redline as fast as possible
3.
A llow engine to fully return to idle (empty the man ifold of pressure)
4.
Re-snap throttle again to red li ne
5.
Record initial peak voltage and redline peak voltage
5
J run~nw
15
Analog MAF Sensor Scope Testing
(Return)
96 contour 2.0, dirt MAF
,..---.,.-------""-,---""----~
.
.
4
.~
.
3 . ..
2
... . . . .
.
: .. .
. . ,
0
G
. . . ..
..
·i · ~ ····· 1
..
.
m\~"·lf~'frlrf1T•'I'" ..
....•
.
....
.. . . . . . . . . .. .
.
.
'
;·
...•
:
.' .......
:
. . . ..
.:
.
:
1 .
'
·: · : · · ·· ·· · · · · ( MMJ.:a~,,11~1d&i~\w~
.,
.
96 C.C>.llt.C>ur after c leaning
.
.
,__
IM_a_tc_h_
in_it_ia_l_v_o,...
lt_
a_
ge
_
sp
_1_
'k_e_h_e_
re_-.--~ 4 .
~. /
3
5 . .................
'
•
The goa l in these captures is to see peak MAF voltage . Performed during a rapid WOT
snap .
•
Because this engine has a rev. limiter achieving redline in park is not possible
•
To see peak MAF voltage on an engine with a rev. limiter you must do the following :
1.
KOER with a hot engine at idle
2.
Snap to WOT as fast as possible
3.
A llow engine to fully return to idle (empty the manifold of pressure)
4.
Re-snap throttle again
5.
Record initia l peak voltage
16
Digital MAF Scope Test
Digital Waveform
Graphed Digital Waveform
'
'
'
'
'
'
'' 1
'
''
'
'
•
•
•
"•
'
''
'
''
6········· ······················~··· ············~············· ··················:········ ·······~···············:·· ·····
0
G
:
' ···························
'
'
'
' ····
·2········ ·······················~···
·'- ··············"'·········
··························
'
'
'
'
'
'
.
'
.
..
'
'
'''
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
20
30
40
50
chA: fre uen kHz
10k
'
'
'
''
I
I
I
I
I
'
'
'''
.
'
'
'
'
'
'
'
'
'
'
'
'
•
60
2.037
70
10s
'
'
''
. ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J' ••••••••••••••• 1 ••••••••••••••• 1. •••••••••••••• J'••••••••••••••• 1' .......................
.
~
'
'
'
'
'
·6·······························~···············~·······························'···············~···············~·······
0
10
0
2.41k
2.46kHz
Notice the glitches in both pictures. Most of the time capturing a glitch in a digital signal is
easier when using a graphing multimeter like the picture to the right. (taken with a snap-on
vantage)
However this MAF sensor was so bad that you could actually see the glitch in the digital
waveform as well.
17
TytJes Of Fuel Injection
0
G
Section 13
Two Main Types Of Fuel Injection
•
0
G
Throttle body fuel injection
•
(TBI)
- Sprays fuel above the throttle
plate
One or two injectors for the
entire engine
Can be low (9-1 Spsi) or high
psi systems
• Some of the low psi
systems had vapor lock
problems on a hot re-start
Intake is designed to carry air
and fuel
- EFE (early fuel evaporation)
systems were still used on
some
Multi-Port Fuel Injection (MPFI)
- Sprays fuel at the back of the
intake valve
One injector for each cylinder
High psi systems
• 30 to 65 psi is typical
• Helps prevent vapor lock
- Intake is designed to carry air
only (better air flow, can be
made of lightweight material)
- EFE (early fuel evaporation)
systems not needed
-
Manifold tuning valves were added
on some intake manifolds to
improve low and high RPM airflow.
Called Intake Manifold Runner
Controls (IMRC) (see pg. 3)
• These are monitored systems
using vacuum or electric
controls and position sensors.
2
Intake Manifold Runner Control (IMRC)
IMRC valve closed at low RPMs
IMRC valve open at high RPMs
0
CD
3
Injector Location
TBI
Fuel metering
cover
0
MPFI
Fuel is sprayed in an
atmospheric
environment
Fuel is sprayed in an
atmospheric and
vacuum environment
WIRING CONNECTOR
tTO COMPUTER)
FUEL RAIL
FUEL INJECTOR
(NOZZLE)
Fuel
metering
-,,,,,,A=~ body
0
AIR ONLY
INJECTOR
SPRAY
PATIE RN
Visual injector spray pattern testing can
be done on TBI systems to check for
flow problems
Injecto r balance testing (see Fuel
Injector Testing section) is done to
check for flow problems. Visual
inspection is not easily or safely done.
4
Injector Designs
Mechanical Injector
Fuel line
connection
WIRING
TERMINAL
0-ring
I
PLUNGER
COIL
WINOINGS
NEEOLE
VALVE
().RING
SEAL
I
Filter
0
G
Electronic Injector
PLUNGER Sl'RING
!CLOSES NEEDLE
VALVE!
COIL
WINDINGS
Spring
Spring loaded closed
Calibrated to open at a specific fuel psi
•
Fuel pressure is what opens the injector.
If the inlet screen becomes restricted
with debris, no amount of injector
cleaner will remove it. To fix this
problem, remove the injector and blow
compressed shop air through the
injector in the reverse direction of fuel
flow or replace the injector.
Injector flow is controlled by varying fuel psi
• Bosch CIS (continuous injection system)
• GM Vortec poppet nozzles
2. Electronic
Spring loaded closed
Electromagnetic field over comes spring psi to open the injector pintle.
Injector flow is controlled by varying the amount of time the injector solenoid is
s
energized. This is known as the injector pulse width.
Multiport Injector Sequenc~·fFI~
What happens with one
shorted fuel injector?
1.
Pair fired -------------------------------------------- Two cylinder misfire
One driver for two injectors
2.
Bank fired ------------------------------------------ Entire bank misfire
One driver for each cylinder head
3.
Group fired ----------------------------------------- No Sta rt
https:/lwww. you tube.com/watch ?v=KF9viLxwJ Nc
0
https:/lwww. youtube.com/watch ?v=3g TL Y6vsxMg
https:/lwww.youtube.com/watch ?v=vmutNjx 7QD Y
One driver for the entire engine
G
4.
See Fuel Injector Testing
section for more details
Sequential fired ----------------------------------- Single Cylinder Misfire
One driver for each injector
To determine injection design, look at a wiring diagram and count the number of injector
control wires. If there is a separate control wire for each injector it is a sequential type
system. See example on the next page.
Note: Early GMs used two control wires for their V6 and VB engines. Although these
looked like a bank fired system they were actually group fired. (One driver for the entire
engine)
Sequential Fired
System
Bank Fired System
To ES
PCM
If one injector shorts none of the
IGN ---4\J------- injectors will fire on this bank. This is
because the transistor will enter
current limiting mode to protect itself
which causes the other injectors to
not function.
INJ 1
fuse
0
0
IGN
INJ 2
fuse
One transistor
"driver" for
each bank
es Refere.....,
Two control wires
Set timing
PCM fuse
(10 A)
-~ B4
6 separate cont
.
wires
~
~
EST
c One transistor
B "driver" for
each cylinder
Computer
Controlled
Coil Ignition
(C31) module
connector
7
Other Injection Designs
Bosch Continuous Injection
System (CIS)
GM Central Port Injection
(CPI) Half electrical half
mechanical system
Fuel
Distributor
Throttle Plate
Poppet Valve
0
0
Injector
Fuel
Control
Plunger
Cylinder Head Air Sensor
Plate
Air Sensor
Ann
lnje or
CFI
Fuel pressure must be at least SO psi to force open
the poppet nozzles so a no start condition will occur
with less than SO psi . Normal operating pressure is
SS-6S, with psi being closer to 6S during cranking.
8
Fuel Delivery Designs
0
G
Section 14
Introduction
0
The main purpose in understanding fuel delivery designs is in troubleshooting
fuel pressure problems. There are design differences that will a affect your
approach and direction .
For example with a no fuel pressure problem , you would treat the mechanical
return and mechanical returnless systems the same. However the electronic
returnless system has more components that must be checked before
condemning a bad fuel pump.
G
2
Mechanical Return Type
Fuel loop
V.t<'''''''
St.llll t.t~
Press Lire
Ga Lige
Pr essL1re
1 -...... RegLiln ror
0
0
R etLI r11
FL1el
Fi I rer
Li 11 e
I 11jec rors
l11le;>I
3
Mechanical Returnless m~
Pressure
G.1uge
0
G
Fuel
Fi lrer
Pressure
G.1uge
Fuel
Filter/Psi
Regulator
lnjecrors
Injecrors
Fuel Pressure Regulator
Fud rump
rud Pump
lult'I
Technically there is still a return , its just not
attached to the fuel rail.
Fuel Tank
4
Electronic Return less ffivr ~
PCM
PressL1re
G<1L1ge
Monitors and controls
fuel rail pressure
Fuel Pressur
Sensor
0
0
FL1 el
Fi Irer
I 11jec t ors
D
FuelPu mp
Driver Module
Pulse width modulates
the pump based on PCM
command
Vari able S peed
lt1lt.'l
tT.11 llt'I
5
Major Components Of The Fuel ~§iterfiJ ~
•
•
•
•
0
•
G
•
•
•
Fuel Pump
- Capable of around 2 times system psi.
- Contains a one-way check valve to prevent fuel from running back to the tan k
Pulsator
Eliminates pressu re pulses created by the fuel pump and injectors.
Located in the tank or on the fuel rail
Psi Line
- Should have equal psi all the way thoug h it
- Starts at the FP and ends at the psi reg . (Return type only)
- Always contains the fuel filter
Injectors
Have a constant supply of fuel under pressure which must be maintained under all
conditions
Fuel Rail
Holds the fuel injectors
- Contains the psi. reg. (Return type only)
- Contains a fuel pressu re sensor (Electronic return less only}
Pressure Regulator
Determines system psi. by opening and closing a "dump" port to the return line.
- Closed =psi increases
- Open =psi decreases
- Vacuum assist regulator has roug hly a 10 psi difference from no vacuum to full vacuum
Located on the fuel ra il, in the fuel tan k, or as pa rt of the fuel filter
Return Line
Retu rns fuel to the tank, un-pressu rized
In Tank Strainer
6
Filters out any debris in the fuel tank before it enters the fuel pump
Typical Electric Fuel Pump
Note the pump check valve
which closes and prevents fuel
from running back into the tank
through the pressure line on
shut down.
0
0
7
Pu lsator/Dam pen er
0
0
•
The Pulsator is also known as a pulse
dampener
•
Can be located in the fuel tank or on
the fuel rail itself.
•
Dampeners mounted on the fuel rail
may have a vacuum hose attached to
it wh ich prevents fuel spillage in the
case of a torn diaphragm. These look
like and can be mistaken for a fuel
pressure regulator.
-
To determine if a rail mounted
component is a pulsator or a
pressure regulator, check to see
if there is a return line. If there is
no return line then it is NOT a
fuel pressure regulator.
Fuel out
Pulsator
••••. 1/4" G ap
.....
Fuel
pump
Fuel inlet
Strainer/filter
Diaphragm
Fuel from
outlet of pump
8
Typical Vacuum Type Fuel P~s'Sur® ~
Regulator
A leak here will
- - - - - - - - - - - - - - - - - - - - - - cause long crank
times and rich
exhaust conditions
No Vacuum
Applied
Vacuum
Applied-
0
G
A leak here
will just
cause a long
crank time
due to rest
pressure not
holding
There are two places a regulator can leak. The diaphragm and the seat
area.
9
0
0
G
Fuel Pump Electrical
Circuits
http://www.youtube.com/watch?v=Rqtfrx-HeDO
Section 15
•
•
0
G
m'V
Fuel pump operation
Ff
f$?A1
During initial key on , the PCM will energize the fuel pump relay for 1-2 seconds on
most systems . After this event the pump w ill shut off until the PCM receives an RPM
signal. This is a safety feature designed into the fuel pump circuit. Fuel pumps should
NEVER run continuously with just the key on . There must be a RPM signa l with the
exception of the 7-wire VAF design early Toyotas used.
Common components
Chrysler ASD Relay (Auto Shutdown Relay) (see page 3)
1.
1.
Provides power to Fuel pump , 02 heater, Ignition coil , Injectors, Alternator field.
2.
Newer systems used a separate ASD and Fuel Pump Relay, however the PCM
controls both with the same driver.
2.
Ford EEC Pow er Relay (Electronic Engine Control) (see page 4)
1.
Controls power to injectors , MAF, ignition coil(s), PCM , control side of fuel pump
relay, and various solenoids .
2.
The control side of this relay is grounded all the time and fed power from the
ignition switch (non computer controlled relay) which takes the load off of the
ignition switch run circuit.
3.
Inertia switch (see page 5)
1.
Interrupts power feed to the fuel pump in case of an accident. Ford and Hyundai
use these devices extensively.
4.
GM oil pressure switch (see page 6)
1.
Is used as a bypass to provide power to the fuel pump in case of fuel pump relay
failure . Not to shut the fuel pump off if oil pressure is low!
2.
Contains a hydraulic switch that closes above 4 psi of oil pressure.
If the FP relay fails, the car will have extremely long crank times, especially cold.
3.
4.
The fuel pump CANNOT be disabled on these systems by unplugging the FP
relay.
5.
Circuit opening relay (see page 7)
1.
Used by Toyota to control the fuel pump.
2.
Contains two separate control circuits . One is energized during cranking and the 2
other when the engine is running . Th is relay was developed originally because
the ECM did NOT control the relay. The VAF did.
(Return)
Chrysler ASD Relay
ASD Relay~
Fused B+
PCM
0
G
~-6
Power to:
Injectors
_ _ _ _ _.. 02 Heaters
Ignition Coils
Generator
Fuel Pump (older designs)
What's important to remember when dealing with Chryslers, is the power to the
injectors and ignition coil(s) will NOT be there with just the key on. These circuits
are tied into the fuel pump circuit and operate off of the same principles. There
must be an RPM signal for this relay to stay energized.
3
Ford Fuel Pump Diagra r1W~
(Return)
HOT IN START OR RUN
HOT AT ALL TIMES
18
FUSE
O BLOCK
~:::J
0: FUSE
o LINK
POWER AC INPUT
>
S151
DI
361
R
":I'!
0
I
840 I
z
RfT
640 I RfY
Il
I{-- -3 l~~ITY
37 y
I
640
RfY H
FROM
A/CHEATER
361 R
C222
C105
1
381 R
TACHOMETER 940 RfY
WARNING
1
INDICATORS
1
UPSHIFT
INDICATOR
37 y
787~K/BK
:rr.
347ilBK/Y
C126
361 R
C256
787Ji"K/BK
97
361 R
TILG
1
I
C300
347 : BK
347 : BK/Y
PK/BK
1
I
940 I RfY
0
0
I
TI
787
I}-------}l!~~A\R
C254
INERTIA~
SWITCHI 19
OPENS
ON
T
-
IMPACTL 1_
I
I
C255
11
SOLID STATE
....!.. -
PK/BK
57: BK
57 BK
I
I
T
I
f
S153
S7IBK
57: BK
I
.A. GRD
ELECTRIC
FUEL
PUMP
SEE GROUND
AT RIGHT
571 BK
.*.0101
-
-
I
J
2
ELECTRONIC
CONTROL
ASSEMBLY
EEC
POWER
RELAY
DIODE
57 BK
57
L-~-..:
S~1S-3~~~~~B~K~~__J
BATTERY
t
-
12
57 BK
787
C254
~·- -
57 BK
C125
fi7
57 BK
BK
G107
4
(Return)
Don't forget to check this
device when you have a no
fuel pressure problem from
no power to the fuel pump.
Inertia Switch
Open
Closed switch
.... , ·-------...- switch
- --- - Lever
0
Ball
Overcentering _.;..spring
0
0
Electrical~
contacts
Magnet
0
Terminals
5
(Return)
ffiV'~
GM Fuel Pump Circuit with Oil Pressure S-witch
0
Fuel Pump
Relay
To Oil
Light/
Gauge
0
@~ ID
---·
-
Hydraulic
switch that
closes with 4
psi of oil psi
Fuel Pump
Test Lead
6
Toyota Fuel Pump Circuw~~
(Return)
~ ~ §fl3:£
_,
1111~1 M ein Relay
EFI
15 A
-
KOE O, jump these two pins
together to force the fuel pump to
run
/
~
-
'- _....
'"
8
I I
Oaca Link Connect or 1
lGN
75 A
lgn 11on S\vrtc h
0
AM2
-
AM 1
-
11 ·2
-
•AM1
AM2
I
-
*B
- "o
~ ALT
100 A
'
MAIN
FL
~ ~r
-
Clu tch Stan
Sw itch (M IT)
40 A
JOA
0
,
Fuol Pump
-•
-...--
....
Park/ Neutral
Pos111on SWJtch
FP
~
---
ST MAIN
30 A
STA E1
l
j
T
• Bateery
.,._
-
--
-•
ST
Rolav
FC
or VAF on older
systems
Relay
)
Opening
To ECM IFCJ
Start01
:
Cucu•I
-
10 A
---
--7
1992 Jeep Cherokee Fuel Pump Circuit
With the engine
cranking or running the
:LLJ'~':,> ASD and Fuel Pump
Relavs
will be
•
energized
•
Too only pt1rpose for 1his destgn
0
G
.....
•;;.;W
;;;;.c......, - ~'""-"D _1_~•:.tiDll.D ~~
was to reduce the noise of the fuel
T •tL LTS) C'00....'4 C..C)
"
pump. During cranking and WOT the
GMO>UNO I LM»*W •109
OOw...) ~MIS&OK•91
fuel pump was provided full battery
N SzEb
O
voltage. All other times voltage v1as
reduced through die ballast resistor.
This was a poor design and only -+...a..~~----.:::"":.:z::•:.,...tto:::.:::._:..:
1..1secl In a fev1 years.
°""
• u.J
aCL.a~•
...-r
'--+--+--ti--..:;-..::..:=:..~
CllCC-- au<
•
-EL~K
ViltlT
••• I
A8T
. . . . . .'T1Qft
~Vilh the Ballast Resistor Relay
To 02 Heaier • ,
•
•
off lhe fuel pump ii; Jed pm\-er
lhrough 'he ballast resistor
mich drops volt.age to 11ie
pump. VV!th this relay on, lhe
balatit resistor i!!. bypassed
and the pump is supplied ful
battery voltage
8
mV'~
@
1997 Pontiac Grand Prix 3800 VIN 1 Engine Fuel Pump
Circuit
~------ --- ~~~--- ----
l
LTGRN
0
0
A(!?-~
PUMP
FU SE
.,___ __
1C>A (
_
l
I 2 J--0 Ii~i:.;C>NT
GRY B-{ I?--'
FUEL PUMP
RESISTOR
(RIGHT FRONT
FRAMER.All,
FORWARD OF
- 3 ""'-
L ... 1..- - -
z
FUeL
~
::R rvt f'tA.L
PUM~
PRlrvtE
FR ON T\MiEE~
~
~
~
~
....
.....
...
&
--
_ll
_
,.L _. 1 ~
- :s;~L..-.I_
s;;: __,o
..,....e ,,,. r.> /
~"T~
c;
~
~
<O
""'
l2~
~
ll,.Q
!::>
With both relays
"on", the fuel pump
is fed power
through the resistor.
With just the fuel
pump relay "on",
the resistor is
bypassed and full
battery voltage is
applied .
1~~
~
.._
ca-.
!::>
• .e.r:~------~-----+------:------4-----1--4--'
-
,___ _ _ _ _ _ _ _ _ _ _ _
__
~
•
..
~
n~M Y
.._..~R V
,..______________,.
PCM control -...-.5t._!,~~RN
__ ,_ ---,_
GR'( 8
L- ---,
C
I
11
PCM control
1-I_
I
M
I
BU<
_~
c( I
:
Ln.e:_F\.I~
__
ruEL 'IAllK
9
1998 Pontiac Bonneville 3800 VIN 1 Engine tlJaiM:>urrii] ~ ·
Circuit
0
This is an updated version of the last example with the
resistor being eliminated . This is still a variable speed
pump using PWM principles.
...J
~
:::>
~
1:1
.;•
0
G
[Bl:!fMl LEf
14CI< Pllt~a
TRIM A.J.TE)
~1{1]
T
~
,.:;a..
11.
...J ~
~b
... ...J
':.::"
c..
~
a..
~J:
~
0
11:
~l
..JO
11.l
w
_w
::> 0
...J S'
IP - - - ~
(\Im 1)
JUt>CTION I
~
(FRCHT !HT
[10CV I
...
•..J
~
..."'
(Ill
,
£in
·-..."'
-r---
I
LFUElF\JhP~
-
r
u
2
~I
M I
------------
I
I .----..--------,..--.
'i
' FLIS I
I
________ (::: I
I
•.
I
...._~-----.'---'
I
.a
I
_m _ _ _ _ I
"1N 1 ,!.,
ct
I
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mI
I
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e
...~
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:II
Cl)
..,
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c~mcx.
a..~z MCOULf
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en
~
--
f Ul:i.
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... i ...... ~~ LUG(IA';E
SIDE~
... rr~em
z
rl.
~
(L.
FRct-1Fl.El.J\Jl\f'
FUSE&
(DIAGAA\4 1Cf 41
----
VINY.
\
~
I
Ill
0
• S273
i:
'~
•.
l~L!A'T~
~
C~C.,rut
-
~I (FRONTOFENJ,I
I D(MfR SfCIRINI
,~or...A
-!- G125
u
t
-
PCM control signal
10
2002 Ford Taurus Electronic Returnless FuWS~ter® ~ .o
- - - - - - - - - - - - - - - · · - - -,a,... l 't'MY
fU,. 6 I .11.•..:-nOP<
~
1 •C9<
SJA
1~•10
l'\JCl
----. .r.
l'ICLA~
"''"""'
-\
I
.
:
""°~
.. --i.. ---- -; ---J
·1- --..! --3
.. ,
~
• • tA ;
I
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o
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(Uf'T MCAA 0 r 0«11. . CQl.Jl>T)
'''"° --+
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I C0>..9Tj
-
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r"'1l,l1'Tf}"
• .
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i
.
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I
Fuel Pressure Sensor (Electronic Retumless Fuel System)
Electronic rctunlless fuel system docs oot me a f'ud pressure regulator Electronic rctumlcss fuel svstcm uses a Fuel Rail Pressure (FRP) SCllSor to sense fuel Jl!C$SU!'C
FRP sensor is locmed in fud injet:tion ~ly mruiifold as~o!Ulbly. FRP ~ iapttt sigpal is used by tht PCM to vary tht duty cyclt output ro ~ Fud Pump Dri\'cr
.Module (FPO~ to compensate for \'aryiog loads. FPO~ thto modulates voltage to fud pump to achle\-e proper fuel prtSS\11~ Engioe Fuel Tewpmll.A't (EFI) sa1SOf
input sigaal ls ilho U5td by PC.M to vary fuel prtssure to a\'oid fuel systtw vapoiiwion..
Fuel Rilll Pulu Dilm~r
http ://www.youtube.com/watch?v=Rwve61Xri04 (Part 1)
http://www.youtube.com/watch?v=u3421RRJ5bk&feature=relmfu (Part 2)
NOTE:
Fuel rail pulse damper used on mechanlcal returnless fuel systems should not be confused with a fuel pressure
regulator. Both are vlsually slmnar, but the fuel rail pulse damper does not regulate fuel pressure. Damper Is used to
reduce fuel system noise.
Fuel rail pubc ~is kx:atcd on tht fuel ln)('l;tion supply II1ilWfold Bild reducCl fuel system noise call5Cd by the pulsmg of fuel injectors \'aarum PQft OD f'ud rail pul:ic
d.'!lllpCI' is coonectcd to manifold \"aCUIJlll to avoid fud spillage ifd"mpo:r diiipbrngm ruptures.
11
2000 Ford Contour Electronic Returnl~'7s9=ue'1 ~ ·
System
----------------,
FUSE
FUSE
FUSE
0
11
20A
41
20A
2
3
1
I
9
15A
I
I
3
I
I
I
I
FUEL
POv1
PO\ll.ER
RELAY
3:----
P LtvP
RELAY
I
----
2
5
----
...
::.:
C>
u.J
~
u.J
~
~
=
a::
a::
0
...
::.:
~
~
a::
-----
(!)
(!)
--
1
5
::::>
(!)
Ee
=
a::
=
a::
~
(!)
I
______ J
a::
Q
(!)
S3003 •
G
0
0
a::: a::
Q Q
=
I C a::
=
0
0
1
'
--
All of the following scope
pictures relate to this system.
.,.-,,
RCla IAFlJIA
SHUT-OFF
SWTot
Fue l P ump Module Control
and F-dbaek S i gnals. Botti
of t h e - ~res go to ttie PCM
on pins 40 and 80
FlJIEI PltctlP
t«JOl.9 E
FlJFI "YANK
(lEFTFRONr
(UNDER
l.9'C"T
12
v
v
v
20
-- --- -.... --- ---- --- --·- --- --- --- --... -- --- --- --- -.. - --- --- --- --• - --- --- --- --• --- --- --- --- ~ -- --- --- --- -.... --- ---- --- --·- --- --- --- --... -- --- .
16
.
•
2.0
'KO
EO
'
- -- - -- ~ ------------
-~
•
20------~-' . --. -.. --. ---
.
• • • • • • • • • • • • ,. • • • • • • • • • • • • 9 • • • • • • • • • • • • T • • • • • • • • • • • •
''
·
..
''
'
0
G
0.8
0.4
~
.
• • • • • • • • • • • • -.- • • • • • • • • • • • •1• • • • • • • • • • • •
''
·
''
-~
''
_________......___......__...,.._..,....,_____
I
I
I
I
Fuel Pump Prime :
:
:
:
I
12
I
:
:
.
-----------: ------------.--- -------:- ---------Air ·p-icr.:fres··tak-E!n:·al lfle ·fp----------·: ----··
'
\•
I
1.2
''
-----------<.--- - -- - -- - -- ~ -- - -- - -- -·F-
I
1.6
v
• • • • • •
• • • • • • - . · • • • • • • • • • • • •1• • • • • • • • • • • •
'
I
'
I
'
I
'
I
I
8
I
module iri the trunk. The module
l 6-. -. K~y· Olf .... -- ·· ··· ··· ··-:· ·· ··· ··· ··· · ·· ··· ···· ·!· ··· ··· ··· j s' ·ted ·Jj(jWer·tro·rr.-:·ttf e ·Fp · te1ay·-· --·:· ·· -·· ·20
•
•
ttiru the inertia switch. The
12-- --- - ~- --- ---. --. - -:-ll>'---+--~-+l - --------. -: . --. --. --·module-s uppties ·ii owe r to· ttre---. ---~ -. ---·16
'
'
'
~
'
'
.
fuel pump KOEO and KOER and :
'
'
'
'
.
'
8~------.-------------·
·
·
·
-·
--~
·
·
·
·
·
·
·
·
·
·
·
-~
·
·
·
·
·
·
·
·
·
·
·
·;
·
·
·
·
·
-·
--·c(>ntro·ls-t:ne--FP
·g
t
ottn·d
-to:-co
ntrol~
-· -·· -12
·
'
'
'
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
.
4
0
.
0.0
-4
8
-8
-0.4
o-..... ,_• .......... .
4
-12
-0.8
.4 _ _,;__ _ _..J='.:_-:_..,.__,..,_..,.__,..,_..,.__,..,_.:;_,,..,_..,.__,..,_..,.__,.,_..,.__,..,_..,.__,;,,..,.__,..,_..,.__,..,_..,.__,..,_..,.__,..,_.;.._!--:_..,.__,..,_..,.__,..,_..,.__,..,..!
_ -f- · - --- --- --- , -- --- --- --- - ~ - --- ---- --- -"-.""
- _..,._.,..
__..._...______...._-~' -- --- ·O
-16
-1.2
•
'
-0.5
0.0
0.5
.
1.0
'
1.5
2.0
'
2.5
.
3.0
A = Fuel Pump Current (1 OOmv/1 amp) B = Fuel Pump Ground Voltage
C and D PCM to FP Modul e control and feedback signals
The FP module controls pump ground. Initial KO prime.
'
3.5
4.0
·20
s
=
13
JIGI ~ X 500 ms/div • x20
A t. 2 V
Bf t20 V
v
0
C :t20 V
xl
:::J[ciC::]fxl:::J DI:t 20 v
fx1:::J
DC•
v
v
r- - -- - - -·- - - -?· · - - - ··· --- · ~ · ---- · ·---- - ~ ----- - -- - ---,-------------,------------- r - • •---- · ·---r •• ---- ··· ---r •• ·-- ··· ----· · ---- ·· ----- ~
20
'
Fue l Pump Turne
d
'
I n i ·la I· Al"ln;lA
. . ·········;'............ ;'
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16
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=Fuel Pump Current (1OOmv/1 amp) B =Fu el Pump Ground Voltage
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925
950
975
1000
1025
1050
1075
1100
1125
1150
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A =Fuel Pump Cu rrent (1 OOmv/1amp) B =Fuel Pump Ground Voltage
C and D =PCM to FP Modu le control and fe edback signals
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ch C: Frequency(H z)
149.9
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50.16
FP
ch D: Frequency(Hz)
0.9997
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50.00
WaS . 61 VDC.
A = Fuel Pump Current (1 OOmvn amp) B = Fuel Pump Ground Voltage
C and D =PCM to FP Module control and feedback signal s
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5.0 s
-20
Sensor reading
16
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ch C: Frequency(Hz]
149.9
ch C: Duty cycle low(%)
50.16
ch D: Frequency(H z)
0.9997
ch D: Duty cycle low(%)
50. 00
A = Fuel Pump Current (1 OOmv/1 amp) B = Fuel Pump Ground Voltage
C and D = PCM to FP Module control and fe edback signals
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2520
-20
2525ms
Cranking,
zoomed in
17
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ch C: Frequency(Hz)
149.9
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26.77
ch D: Frequency(Hz)
0·9998
50 .00
ch D: Duty cycle low(%)
Fu el Pump Current (1 OOmv/1 amp) B Fuel Pump Ground Voltage
C and D PCM lo FP Module control and feedb ack signals
Th e FP module control s pump ground. KOEO
=
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18
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ch C: Frequ ency(Hz]
149.9
ch C: Duty cycle low(%)
26.7 7
ch D: Frequency(Hz]
0.9998
ch D: Duty cycle low(%)
50.00
Fu el Pump Current (1OOmv/1amp) B Fuel Pump Ground Voltage
C and D =PCM to FP Module control and feedback sign als
The FP module controls pump ground. KOEO
I
I
I
~
I
2600
I
2625ms
19
Fuel Pressure Testing
0
G
Section 16
Fuel Safety Concerns
•
Always depressurize a fuel system and remove gas cap to relieve
tank vapor pressure before removing any fuel system component.
1.
Disable fuel pump and crank engine for 10 seconds.
•
•
0
G
This will NOT work on CPI systems with mechanical injector nozzles.
Removing the fuel pump relay will NOT disable the fuel pump on early
model GMs due to a bypass through the oil psi switch. Also some
systems use the fuel pump relay to feed power to the injectors.
2.
•
•
•
Relieve pressure using the pressure test port (if available) on the fuel
rail .
Never use incandescent drop lights when working with gasoline.
Never manually energize an electric fuel pump when removed
from the tank.
After repairs or testing, before starting the engine . Prime the
system by cycling the key and check all connections for leaks.
2
Initial Testing
•
Return type with vacuum assist regulator
1.
2.
3.
4.
0
5.
G
6.
Check for prime (should equal WOT psi after the 151 or 2nd prime)
• Some systems do not provide a prime
Start engine and check idle psi (usually 8-10 psi less than KOEO or WOT reading)
Remove vacuum hose from the regulator to re-check WOT psi.
For low power or lean exhaust codes perform a WOT snap to redline (do not over
rev. engine) while monitoring fuel pressure. Make sure psi does not drop off during
acceleration. This is a volume test. If the injectors are spraying heavy and the fuel
pressure stays normal then the pump volume is good. (see pg. 5 case study)
If pressure is low, check pump max psi (block off return line)
• Should be around two times system psi
• Use this test to determine if the fuel pressure regulator or the fuel pump is
bad. If pressure jumps up to near two times the system pressure then the
regulator is bad. If pressure stays low then you have a pump problem.
Test drive while watching 02 mv at WOT.
1. If fuel delivery is good the 02 will stay over 800 mv the entire WOT duration.
2. If fuel pressure drops under load the 02 sensor will go lean however this is not
the only cause of a lean condition at WOT. (A dirty MAF sensor is the other
common cause of a lean 02 at WOT)
http://www. voutube.com/watch ?v=-5L5tp4NDq0
3
Initial Testing
•
Returnless fuel system
1. Check for prime (should equal system psi after the 1st or 2 nd prime)
•
Some systems do not provide a prime
2. Start engine and record idle psi
3. Snap throttle to redline rpm (do not over rev. the engine) make sure
psi does not drop off during acceleration . Again this is a volume test.
(see pg. 5 case study)
0
4. If pressure is low there is no way to determine if the cause is a bad
pump or bad regulator (tank mounted regulators only). They should
get changed together as one unit.
G
5. Test drive while watching 02 mv at WOT.
1. If fuel delivery is good the 02 will stay over 800 mv the entire
WOT duration. http://www.youtube.com/watch?v=9TlygJMxTps
start watching at 1 :40
2. If fuel pressure drops under load the 02 sensor will go lean. (this
is not the only cause of a lean 02 at WOT) watch this video
http://www.youtube.com/watch?v=Hmt LNJ9Gkl In this
there is not a fuel pressure problem but it is the same test.
video
4
(Return)
Snap Throttle Example
Freeze Frame Data
nglne Coolant Temp
Vehicle Speed
Cale Engine Load
Fuel Sys Status Bnkl
Fuel Sys Status Bnk2
Long Term FI Ban k 1
Short Term FI Ban k 1
187
28
4 0.0
C l ose d
Disabled
2 4 .2
25.0
Note the fuel trim, engine load
and RPM. What is causing this
lean condition? Its not a
vacuum leak!
Use freeze frame data to determine type of lean cond ition. A vacuum leak will effect the low
R PM ranges more and a fuel pressure problem o r dirty MAF sensor will affect the high RP M
ranges more. See " Oxygen Sensors and Fuel Trim " section for further information.
0
G
5
Fuel Pressure Too Low ffi~ ~
~
(Mechanical Return or Returnless System)
0
G
•
May be caused by:
1.
Bad/weak fuel pump (most common)
2.
Restricted in-line fuel filter (change the filter and retest pressure)
3.
FP power or ground problem
4.
Debris in the tank (restricting sock strainer)
5.
Stuck open psi reg. (opening too soon) - not common
•
Perform the following with engine running:
Check FP power and ground
•
If power and ground is good then replace fuel pump and include the
following:
1. Always change the fuel filter and sock strainer
2. Always check for tank debris with the tank removed.
3. Always test the sending unit wires for opens and shorts. In particular
when you have no fuel pressure, no current flow to the pump and a good
power and ground.
Return type systems only
•
If possible, pinch or block off return line to check pump max pressure
1. If psi immediately increases to around 2x system psi suspect regulator
problem
2. If psi stays low you have a pump problem (check powers and grounds)
6
Fuel Pressure Too High
(Return Type System)
•
•
0
G
May be caused by:
1.
Sticking closed fuel pressure regulator
2.
Restricted/pinched return line
Perform the following:
Remove return line from the fuel rail and run a new line into an
approved container
Retest fuel psi (if possible don't start the car = fire hazard)
•
Psi still too high = stuck shut regulator
•
Psi now normal = return line restrictions
*NOTE* a leaking or broken vacuum hose to the fuel psi reg. will cause
normal WOT psi readings but higher than normal idle psi readings
7
Fuel system rest pressure tesqijtt§
•
Pressure drops on shut down
-
Pinch off psi line
•
-
G
Psi now holds = bad pump
check valve
Pinch off return line
•
0
http://www.youtube .com/watch?v=AKtR yF7bi8
(Ruptured Regu lator Diaphragm)
Psi now holds = leaking
pressure regulator seat
With both lines pinched and psi
still bleeds down you have either
an external leak, a leaking fuel
injector, or a ruptured regulator
diaphragm.
•
Symptoms caused by bleed down
problems
-
Long crank times (only}
Long crank times and a rich alt
ratio, if the bleed down is due too
a leaking injector or a ruptured
fuel psi reg. diaphragm
http://www.youtube .com/watch?v=09 wQ9yQ85A (GM CPI leak-pa rt---1)1-·'""
b ttp ://www.youtube .com/watch?v=dAAFM3zlJME
(GM CPI leak part 2)
8
Fuel pump power and ground teSQ.J.Fl!jl
~
http ://www.you tu be .com/watch?v=C Ejmo g T4 yQ
http://www.youtube.com/watch?v=rQ7tvlxQSt0
http://www.youtube.com/watch?v=Q3ZiTsKCd08
•
0
G
Voltage testing (loaded circuit)
http://www.youtube.com/watch?v=McnXLcJNVfl
To energize a FP circuit when the car doesn't start from no fuel pressure
perform the following:
1. Manually energize the relay or pump (using a test light or fused jumper
wire), With the relay removed , jump the load side with a fused jumper
wire. Never jump the control side of a relay!!!
» (Bosch relay, Load side = pins 30, 87 and 87a. Control side =
pins 85 and 86)
With the relay still plugged in, energize the control side with a test
light. "be the computer".
» You can also use a jumper wire to energize the control side of
the relay, but you better not get your polarity mixed up. If you
provide a power when you should be providing a ground or
vise-versa, you will fry the transistor in the computer. (see
"Output Solenoids and Transistor Drivers" section for more
details on power and ground side switching)
2.
Command the fuel pump to run using scan tool bi-directional controls.
The purpose of manually energizing a fuel pump instead of just cranking the engine
over, is by the time you find a good ground for your voltmeter and locate the correct
wire to test, you will have overheated the starter and killed the battery.
9
Fuel pump current testin gn~ ~
•
0
G
~
Connect amp probe to one of the following locations
The fuel pump power or ground wire, either at the relay or at the tank.
1.
GM fuel pump test connector. Jump directly to battery(+) with a fused jumper wire , and
2.
connect amp probe to jumper wire with engine off. (see pg. 12)
3.
On a system with the FP relay in a power distribution box, you can remove the relay and
jump the load side pin contacts . Install you r low amp probe around your jumper wire. This
method is very dangerous in that if you jump the wrong pin contacts you may fry the PCM
fuel pump relay driver.
•
Measuring pump rpm
Determ ine the time interval between un ique "humps" (one full revolution of the
pump), automotive pumps can be 3,6,8, 10,12 ,and 14 bar pumps (8 and 12 are the
most common)
Divide that number into 60,000 to determine rpm
Typical pump speed is 4000-6000 rpm (see pg. 11)
•
Measuring pump amp draw
TBI - 2-4 amps
PFI - 4-6 amps
CPI - 8-10 amps
•
High er than normal amp draw
Restricted fuel filter
Defective fuel pump
Defective fuel pressure regulator (stuck closed)
Restricted fuel lines
•
Lower than normal amp draw
High resistance connection
Bad ground
Defective fuel pump (poor brush contact or mechanical pump failure)
10
Defective fuel pressure regulator (opening too soon)
Measuring fuel pump RPM
''
'
•'
••
•
••'
10 -
•
•
-
•
••
MiA
.
.
•
•
•r
50
Aux LoAM
"""
I
"
1. look for unique 1mmps" to determine one
complete 1wmp motor rotallon.
2. Measure the time in milliseconds it takes for one
rot.itlon.
3. Olvl~ e this number into 60,000 .
••
••
•
••
•...
2 0
Sync
Lock
~
•
•'
•
•
•
•
••
•
''
~
cur.sers placed at unique humps
•
to measure the time it tak !S for
one complete revolution c f the
•
pump motor. This measu ment is
45.,• m.s.
4 ••
•
•
•
•
•
•
0
k
1, \1
'
8 -
6 :.
'\~
~V: ~
-: ~~
•
This Pump Is Running At 1330 RP~I.
{interminent no.start no fuel pressure. picture was
taken aher hining on the fuel tank, ps'i went to J6
psi)
.
•
.
.
I
100
Patternl S1o1ee
250 MS
,
•
•
•
Scale
10 A
•
.
.
I
,
.. . .
150
FraMe
0.00
,
.
.
I
200
MS
250
Movie
Off
Cursor
Both
11
(Return)
Jumping a GM Fuel Pump Test Co rcote~tor~ ~ .o
0
G
Scope not shown in this picture
12
0
G
Low fuel pressure, long crank time, intermittent no-start. What is the fuel pump RPM?
13
f$?A1
'7 :=!
Fuel Pump Current Examp~es
84 VW Rabbit, hard starting, poor performance, lean misfiring
v
x=q1,Jl111s,o=OJ.111ms..xo=1t,qlm$
11
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40
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8ll
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11011\
A' lucl pUlllppower @11v B' Juel pumpcu11"'1
1maxluel po @60 psii Rl'M' 3651
4.0
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4.4
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A' fuel p""' p..ei@ 10.91 B' loel pump cunt~
!max fuel p!i @60 psil RPM ' 30l3
13Feb2006 11:13
I
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80
3.6
3.1
90
1.8
100 ms
The main purpose of these captures was to illustrate the relationship between voltage
and current. Notice how much difference a one volt increase makes
14
Case Study
2000 4 .3 Vortec, no drivability
problems. Good psi and volume.
2001 4. 3 Vortec, intermittent no start
A
v
A
16
20
18
16
16
11
10
0
G
11
A
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1001 GMC0 htl f\Jmp Cunc~. l'!cssurc ~ 51 @idlc"d 61
@WOl.lolennitttntno ··~~. Max psi'"' 80 psi.
11Sep2006 1 ~6
Open in one of the electric
motor windings
14
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The main point with this type of testing was being
able to identify the cause of the intermittent no start,
even though the truck started every time / looked at
it. This problem could have NE VER been identified
with conventional testing methods. Only if it was a no
start during testing could you have accurately
identified a bad fuel pump.
15
so
Fuel Pump Current Flow Case
Why is the voltage dropping to the pump? Because the amperage is ridiculously high
from a shorted pump. Remember if the wire used to run a component is carrying
excessive current, the wire will heat up and act as a resistor therefore dropping voltage!
Copper wire increases resistance with temperature. I have seen 4 volts on the feed
wire to a shorted fuel pump and there was no wiring problem. It was simply the pump
drawing 20 amps on a circuit only intended to carry only 5 amps.
16
14
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12
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20
40
60
uo
A = t ucl pump current
100
120
140
8 = f lJCI pum p powe r
160
180
-20
200 ms
16
Fuel Injector Driver Designs
0
http://www. youtube .com/watch?v=4mut0Lpg5k4
G
Section 17
Two Main Types of PCM ln~Cfor (ID ~
Drivers
1. Peak and Hold
2. Saturated Switch
-
With all electronic injection, the speed at which an
injector opens affects fuel delivery
•
0
G
To quickly create a magnetic field that's strong enough to
open the injector pintle (that has system fuel psi behind it),
without overheating the injector winding.
- Engineers must take into account:
» Variations in system voltage
» Injector resistance and current flow
» How fast the magnetic field builds to saturation
» Time it takes for the pintle to open and close
» Size and flow rate of the injector
» Fuel pressure differential
» Maximum operating frequency
2
0
Injector Driver Designs ffivr ~
Peak and Hold
Saturated Switch
+B
+B
+B
Solen<>ld
ReslstOf'
Low
High
Resistance
Injector
ECU
ECU
Resistance
lnlector
ECU
0
0
A: 'lnlnslator On
8 : Injector Open
'I
I
: "'MMN\Nll.M/IJ'1
I
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A
8
A
B
A
B
3
Saturated Switch Waveform~
[d[ili ~ x j20 ms/div :::J •
3 AJ~5oo mv
..::] J o e ..::JDx2 ..::] cJ.ott
s r -100-400V [x201:::Jlo c 3l{x5
mV
:::Jllo c
· I Off •
:.:J ofr-o-ff--==----- :.;n DC • Io tt :.:J
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e re~ o
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300:·waveform·-·-·---·: ·-----·-------:--······-·-·--:····-·-··--···:·-·-··--····-·: ··-----·--···:-····--·-··--·:··---··---····:·-··----------:r o
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______________ :______________ : ______________ : _____________ : ______________ ______________ ; ______________
.:
.
:
Should: be battery
:
:
:
Pin tie hump, shows
:
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ol-....YRl.t.<! 9.~l h~-~~. ....... -..........! ~~-':'~ i_~!C:!..... j..... -........ j.! ~~-':' ~ i_~!C:.i;........ .-... ./· .. rn~.«ti.~ni.«!lJ........ L..............ho
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:
"or-"
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~
movement
:
:
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l..I ........... l.1ni·ecto~.''.o~.time''. ..... [ ...........................L. ·-· ... ·-·... j__ ............ Lo
:
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: or pulse W.idth
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·-------t-' -------- ----t--------------t------~ ~.
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100; 100 mv= 1 amp
'
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!Ramp with !no
o'.
:
:
:stra1
d"ght. udp.:line =
:goo win 1ng
:
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tyP,ical saturat~d switch in:j ector
t.1-----···· ----l--······
!
'.
10
.
.
.
:
:
Should be near ground :
:
-5o; ... Current. ........... ;.............. :........ ···· ·vo
: · lta ge · shoi.,s
"""rQ und ·: · · · · · ... -P.-intle-h-Ym!'>-,· shows. ....... i .............. ~20
Y"::J
mechanical movement :
:
Waveform
i ~teg rity
•
•
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-1 0 o-. --------------.. --------------.. ------------. -•--------------•-----. --------•--------------•--------------•--------------.. --------------... -------------.-. 3 0
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.
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143
144
145
146
I
.
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!
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I
I
!
I
147
148
149
150
151
152
'
A = Injector Current (
I
I
'
I
153 ms
B = ltl Injecto r Voltage
4
Peak and Hold WavefornfCOJ~
Feedback from an
ignition coil that is
sharing the same
power feed as the
injector. This is
normal.
~/div iJ!xl
iJ A1-10-90V 3 foC3]1 xl 3
s ]-1-9A
3 JDC3Jlx1 3
c]o11
ojott
A
·--r••••••--••••••T""""""""""""""T""""""""""""""T""""""""""""""T""""""""""""""T""""""""""""""~""""""""""""""~""""""""""""""~••••••8
..
..
..
..
·
·
Zener diode "dump" at
:
·
'
.
'
.
'
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A = Inj ector Voltage B = Injector Current
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Peak and Hold
• Peak-and-Hold Driver
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current limiting device to prevent
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overheating of the injector coil. The
current limiting circuit monitors the
current flow through the injectors.
When current reaches the maximum
level, it is reduced to avoid damage
to the injector solenoid. Current is
then maintained at a level sufficient
to hold the valve off the seat for the
required injection period.
With this type of driver, the injector
opens and closes more quickly.
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Saturated Switch
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Saturated Switch Driver
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circuit resistance to over 12 ohms.
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opens faster than a conventional
high ohm injector. (early Hondas)
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Fuel Injector Testing
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Section 18
Types of Fuel Injector Tests
1.
2.
3.
4.
S ingle injectors
Para lle l gro up
•
Effects of one shorted injector in a parallel group
0
0
Sound testing
Noid light testing
Voltage testing
Resistance testing
5.
6.
Visual spray pattern
Scope testing
Voltage and curre nt patterns
•
Saturated switch
•
Peak and hold
7.
Balance testing
2
Sound Testing
• KOEC or KOER
- Listen to injectors for clicking using a long
screw driver
0
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• Touch the end of the screwdriver on the body of
the injector
• Keep in mind that noises transfer and the clicking
that you are hearing could be from the injector
next to the one you're testing
- Listen to a known good one and compare the sound to
the injector you're testing
3
Noid Light Testing
htt~r//www. x:outube . com/watch?v=FAipVwCdwSQ
• No clicking (single cylinder misfire . engine still runs)
Noid light doesn't flash
• Check power to injector
• Check control wire for opens
• Check PCM injector driver
- After verifying power supply to the injector
- Measure voltage at the PCM on the injector control wire, with known
good injector or noid light plugged in. If you read system voltage =
PCM driver problems. If you read 0 volts = open in the control wire
0
Noid light flashes
• Bad injector (in rare cases a weak PCM driver can pulse a noid light and not
G
Noid light stays lit all the time (constant spray from injector, severe rich
pulse the injector)
running conditions)
• Check for short to ground in the control wire
• Check for shorted PCM driver
- Unplug PCM , KOEO noid light goes out= shorted PCM driver. If noid
light stays lit = short to ground on the control wi re.
- MAKE SURE INJECTOR STILL HAS POWER FEED KOEO!!!!!!!
» Some systems WILL NOT have power to the injectors KOEO.
The PCM must have an RPM signal to energized the circuit. So
the above testing must be altered. (Chrysler, VW to name a few)
4
ScopeNoltmeter Testing ffi~ ~
~
(N.C. ground side switched) (single cylinder misfire)
(no pulsing, no clicking)
• With good supply voltage verified, connect
meter to the control wire, backprobing the
injector connector.
- Steady 12+ volts on the control wire (see pg 6 for
[c omplete testing)
0
G
• Open in the control wire (noid light doesn 't flash)
• Open PCM driver (noid light doesn't flash)
- Steady low or 0 volts on the control wire (see pg. 7 for
complete testing)
• Open or shorted solenoid (injector) (noid light flashes)
• Bad solenoid (injector) connection (noid light may tlash intermittently or
not at all)
• Short to ground in the control wire (noid light on constantly)
• Shorted PCM driver (noid light on constantly)
5
:=!
ScopeNoltmeter Testing con .~
f$?A1
• Steady 12+ volts on the control wire
(connector plugged in back probing the injector)
-
Check control wire voltage at the PCM
• Reads 12+ volts = PCM driver problems
0
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- Must check all inputs that affect this driver before condemning
the PCM
» Example - the crank or cam input to the PCM is not
providing a proper signal (such as an optical distributor
with oil in one window of the drive plate)
- Check PCM connector for pin contact problems
- Must check all PCM powers and grounds before condemning
the PCM
- Remember that the PCM will at times shut off the injector on a
cylinder with a catalyst damaging misfire!
• Reads 0 volts = open in the control wire
6
ScopeNoltmeter Testing cLOJv ~
•
~
Steady low or 0 volts on the control wire (connector
plugged in back probing the injector)
Reminder before continuing this chart is that good supply voltage should have already
been verified
1.
0
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2.
Use a test Light
Connect test light to battery (+) and touch on the control wire
1.
Test light on = shorted control or shorted driver
•
Key off, unplug PCM connector (s)
Test light still lit = shorted control wire
Test light goes out= shorted PCM driver
2.
Test light off or pulses on and off =open solenoid or solenoid connector
Check solenoid and connector with an ohmmeter
Use an amp probe
Connect amp probe to the feed or control
1.
Constant current flow = shorted control or shorted driver
•
Key off, unplug PCM connector (s)
•
Key on, recheck current flow http ://www.youtube .com/watch?v=jsl531 -6q -A
No flow= shorted driver (make sure you still have feed voltage
available to the injector after unplugging PCM)
Flow = shorted control
2.
No current flow = open solenoid or solenoid connector
•
Check solenoid and connector with an ohmmeter
7
Ohmmeter Testing
•
•
0
G
•
Single injector
- Connect leads across the two pins on the injector
• Compare reading to spec
- Connect leads, one lead to one pin on the injector and one lead to the body of
the injector
• Should read infinity
Bank or group of injectors http://www.youtube.com/watch?v=3gTLY6vsxMg
- Main injector harness connector unplugged
- Connect one lead to the control wire and one lead to the feed wire (injector
harness side not PCM harness side)
- Resistance readings will always be lower than any one individual injector
• Example G.M. 2.8, 3.1 group fire injection system
- Single injector resistance spec is 12.6 ohms
- Measuring a bank of three = 4 - 5 ohms
- Measuring a group of six = around 2 ohms
Control wire tests
- Open circuit
• Connect leads, one to the control wire at the PCM (PCM unplugged) and
one to the control wire at the injector (injector unplugged)
- Should read close to 0 ohms of resistance on your lowest scale
- Short to ground
• Connect leads, one to the control wire at the PCM (PCM and injector still
unplugged) and one lead to a known good ground.
8
- Should read infinity on your highest scale
Scope testing fuel injecto~~ ~
• A DSO and some knowledge of voltage and
current waveforms will reveal the following:
• Supply voltage to the injectors
• Injector current
• Control circuit integrity
0
0
• Transistor switching and type of injector driver
• Ground circuit integrity
• Injector pulse width
• Injector winding problems (opens and shorts)
• Injector magnetic field strength
• Mechanical pintle movement
9
m'7 ~
~
Scope testing fuel injectors (cont)
•
Voltage testing (KOER or KOEC)
- Connect leads, one lead to the injector control wire and one lead
to a known good ground
•
Current ramping (amperage testing)
- Always zero the amp probe before connecting to the circuit
0
G
- Connect low amp probe around the feed side or the control side
of the injector (polarity sensitive)
http ://www.youtube.com/watch ?v= KArR lg M iGt8
http ://www.youtube.com/watch?v=vmutNjx?QDY
http ://www.youtube.com/watch?v=KF9vilxwJNq
10
Known Good Injector Patter'Ws
Voltage vs. Current
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23 Anr 2003 12:56
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A straight up line in a solenoid current ramp is
a shorted winding
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Description: 92 CiddlJ 4. 9 good l1\J p.allern
Date :
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Pa.t.tern.ISweev
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Why does a shorted injector with double the
=
cu rrent flow not show a large voltage spike?
Answer: No magnetic field from shorted
windings
Ir.
Good ramp caused
by counter EMF
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12
GM Group Fire Injection Case milly ~
•
Symptoms on this V-6 Camaro:
Engine would not idle
Extremely low power
Low engine vacuum
No trouble codes
0
G
•
Starting point w ith the system was to check for shorted injectors . (common problem on GM
Multec 1 injectors is shorted windings).
•
This system uses two control wires for the injectors (One for each bank). However th is is not a
bank fired system, it is a group fired system . (one driver inside the PCM for all of the
injectors)
•
The point of this case study is to show a variable when it comes to injector scope testing. If all
you did was to take a voltage waveform with the scope , you would have determined that all of
the injectors where "firing". Only the current waveform revea led the problem, which was only
three of the six injectors were working. A noid lig ht would have been a better tool than just the
voltage waveform of the scope in this case voltage and current waveforms were taken
on these two control wires individually.
"Blue" control wire
showed a voltage
waveform but no current
waveform.
t
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"Green" control wire showed
a voltage and current
waveform.
•
FUEL JMJECTOfl S
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PNK-BLK ~
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Blown Fuse
?1.11(-~U(
3
(see pages H,
15 and 11.§ for
scope waveforms
OK B LU
PNK-BLK ~ DI< S LU
l'N!<-81.K
s
Di< 9 LU
13
Green Control Wire
(Return)
'\J File Edit Settin11S View Window AIJ:omotive Help
~ [g~ ~ xJ1 ms/div
31
;:Jfoc3 Jo11 31
..
...
..
V~20) •
0.4
325····················~························································································································ 90
''
''
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0.3
300- - -- - -:- - -- - -- - -- - - - -~ -- - -- - -- - - -- -~ - - -- - - -- - -- - -~
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Bank
of tHree
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There is the beginnings of a
.
shorted injector here, but that is
•
•
-0.2 175· .... ·:- ..... - ...... ·:· .. not the main point of this case
study.
· 0.1
0
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200· -•.••:.•••. -•. -•••• .!. •
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-0.4 125· - .. - .;...... - . - .. - . -~ . . ·-. -. ·- ....... ·-. -. ·- .......
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150- - --- -:---- -- . - --- -..:.. -- - -- . - --- - --~ -. -- . - --- --- -~' - -- . - --- --- - -~ -- . - --- --- --.
'
-0.5
100· · · ·· .;•.. · ·· ·-· · · ·· · .;. ·
-0.6
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. ....... ; ............ - : ...... -.... - . ~ ..... -.... -.. ~ ........ 20
1...---...;..-----i-----"T""-----...r-·····--·· ..
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75-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --10
-4
-1
-5
-3
-2
0
1
2
3
ms
A = green wire cu rrent B = green wire volts C = b l ue wire volts
WITH BLOWN FUSE!!!
LJ !Waiting for AOC
Trigger jAuto
:::J jch B:::J l Falli ng:::J EJ~v 1><20) EJ~"
14
(Return)
'\, Fiie
Edit
Blue Control Wire
Settings
View
Window
~D~ ~ x]1 ms/div
Al.Aomotlve
Help
3 lxl
_:J AJ•1 V
-
3 !Oc3 1x2 3 cl-100-4oov 1x201:;JJu c3 )11 ·0
3.(oc:::f~
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90- - -- - ·:· - -- -- - - - -- -- -;- -- -- - - - -- -- - -~ - -- - - - -- -- - - -~ - -- - - -- -- - - - -=-------------~ -------------! - - - - - - - - - - - - - ! - - - - - - - - - - - - - ~ - - - - - - - - - - - - - ~ - - - - - - - - 325
0.2
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0.1
.
.
.
.
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l
;
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1
~ank of three injectors.1
80----- -:- -------------:-------------:- ------------ -:- -------------:-.-------------:-.------------- .
.
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.
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.
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.
.
.
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.
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1Blue tr~ce = c~rrent .
.
.
.
70------:- -------------:------------- -~' -------------'~ -------------r -------------'~ -------------; -------------' ------------- ~ ------------- ~' --------275
.
.
Green ttace = Voltage 1
0.0
60- _-_-_.:-:.::---:_
:: ·_,..,_-_-_.- .-.:-:
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_---~---_:::~----- ------. - --.-- ---;-~- - -----_
______-------:~----.- _______- ----- _- k_-__,..,_-_-__-_-_-_-_
,..,_,..,_-:-:- _-_-,,_,..,
__,..,_-_:_-_-_-_-_: -:::-:-:-:-. ----- ~ ------------- ~ -----. -- 250
-0.1
50- - -- - -:- - . - - -- . - -- - --:- . - - -- . - -- - -- -:- - - -- . - -- - -- - -:- - -- . - -- - . - - . -; - - . - -- -- - - . - -
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.• • • • • • ·······I·············~·············
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How is there a go0d
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. -------. ------. -. -- . . -- . -- -----· -~----- --. 225
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10- - --- -:-- -- - -- - - --- -+--------- -__ ._ --------- --- _._• _-- ---------_.. __ _---- --- --- -------. -----:-------------:.-------------~.-------------;._-------125
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0-·· ·· -:-i. ·· · ·· · · · ·· · .;. · · · ·· · ·· ·· --r---. ··- ·· ··- .r· ·· · ·· ·· · ·· · · r ·· · ·· ·· · ·· · ·
.
. ·· · ·· ·· · ·· · · i·· · ·· · · · 100
20· - . - - .;. - . - . -- . - . - - . ..:. . - . -- . - . - - . - .;. - - -- . -. - - . - - . ;. . -- . - . - - . - - --; -- . - . - - . - - . - .
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- - -- - - ; . -. - - . - - -- . -- : - . - - . - - -- . -- . ~ . - - . - - . - -.. - . ~ -.. - - -- · 150
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·r· · ·· ·· · ·· · · · .; · · · ·· · ·· ·· · .. ; ·· ·· · ·· · · · ·· ·
-5
-4
-3
-2
A= blue wire curre nt
-1
0
B = green wire volts
WITH BLOWN FUSE!!!
1
2
3
4
ms
C = blue wire volts
Answer: Group fired system with one blown fuse to one bank of three injectors.
The voltage waveform seen here on the blue control wire is feedback from the
working bank of three injectors (Green control wire circuit).
1s
(Return)
File Edit SettinQS View Window Al.A:omotive Help
x2
Off •
.
.
W (x20)
.
.
250-.· -· --;--· " " ! " " " " . . . . . - - · - - · - ··-- - · ... - · - - ... - · . .... - · . , • • - •
'
'
'
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0.3
0.2
22
s.:.' ---..: .... ;' .-.--~' .-.. .:-....:'.... -'~ .. -.;_. ....'~ ..--;' .. -. 150
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2o lf";
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'
-----~----~----- ·-- - ~---- 1 25
I
....................
.
. ........... -· -. 100
0.1
17s-; ..... ~ .... ; ___ _
0.0
' --!--·
'
' ---~ -· ---:- -· --:- --- -1-- -. 75
150~- -- --~ -- --~-- -· -}----:-.
-0.1
125-:--- --~ --- -i- -- --:- -- - - ; -- - -. -- - - -;.- . -- ~- - - --:-- -- -.;- . - . -50
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0,3
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.
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175............. ~ ..... ~ .... : ... .
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.... -. . ... -......... -. . -.-so
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f. -- -
'
-0.4
'
.
. -·
·0.1
. . . . .
·0.2 125-:- - -- -; -... -· -:- -- - '
. '
0.0
~--
75~- -- .. ; -- . -~---·l.-'----+--~1.... --... -- --... -- --~- --- , .... 0
Yes we do. This
bank has the
beginnings of a
shorted injector as
mentioned earl ier
'
0.1
'
· 0.3
'
.
'
'
22s..:-----~----;··---~'
150-:-----~- ·--~-.
----r----{-----:-- ---i-··· 25
'
0.2
..
.
.' . .
250.,·····r···-.,·····r-···- .. ---·-.·········-.,·····r-····i···· 175
'
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----: . --- ~- ... -~. --- ~ -· -. -50
.
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1 oo..:-. ---r--- _,_ .. --} ..•. , __ .•
·0.4
75.;.•.. -~----~- · ·• ,.____,___~---· · r •• • • ., •• • •• ,. • • • • ., •• •• 0
·0.5
so.:---.
-.~ ----~-- -- -~' ----.!- - - - --. --'~ ----.:-' --- .;... ---~' -----25
'
·0.6
25~·-·
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.
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'
----r----..:-----}···-i--··
25
'
'
. .
.
'
...... -....... .
.
. - " -. -.... -. ... •• . • •-. -50
'
·0.7
· 0.6
ms
ms
A = blue wire cu rrent B = green wire volts C = blue wire volts
A = green wire current B = green wire volts C = blue wire volts
After replacing blown fuse. Do you see any other problems?
16
Group Fired System Problems
GM V6 With One Injector Driver
For All 6 Injectors
• •
"
A
• OC· II«•
.
B·lO~Olfl(,!IJI • OC •
• v
o.~
0
G
...................................,................................................................
.
0.1 ..................... ""!"' ... ..
'/M!ffi •
.1
One or more shorted injectors
on bank 1 causing this straight
up line in the ramp . This is due
to the lack of counter
electromotive force.
........., .... ······!··· ................. ···50
.
0.1 ....................; ........... ·•- ... ... ... ... ..
.
~.1
-
1
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··· ··
I
2
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4
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. . . , ........ , .............. 60
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.
.................
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.
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.
·······1··············;·····························!········<40
~
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.
....
30
....
~
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.
....
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..
...
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...
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..
..
..
..
..
·OA..................................: ............................................:..............:.............. :.......................................10
·02······:................; ...............;.............. ··························· ...............;...............;............................. ;.........10
'
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·3
'
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0
1
J.: itj. wntnl
-
Bank 1
.
.
..
..
.
·0.1······~··············r·············1································· ......... ·~·········i·····························~········~O
.
............................; ............- - - -· .........................;............................ 9
··
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.....................................•;..............:..............:.............................•.........79
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.
.......................................;...............;...............;...................................... 80
....
....
....
:
:•
0.1······~··············1··············1······················ ····················1·\
. ... ··~· .........; .................... ··· .10
.
..
. . . . ..... . ...... . . .. . . . .. . . . . .
02······'.··············'.··············:·······································/ ,. .............: ·············:·····························; ........ 59
..
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0.0,......,.. .... ,•••,.•• ...,,.,...,.....;.,,,,.,....,,,,.....,,., ······· ····· ····· ·· ····· ····· ···· ·· ····· ····· ·· ····· ····· ·'. ··· ·· ····· ····· ·· ····· ····· ······· ··· ··lO
~
v
'
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1
3
4
5
6
.,
B =inj. whigc
idnQfu•IOC ldotod1tw.ot·lt1bU ·ILIFalino•:Jl.:vwml·3• I~
Bank 2
Notice the weak voltage spike is seen eve on the good ban k. This is because there is
only one driver in the PCM .
17
SEFI Cadillac Case StudyDJ~
'\! F;le Edt setth;IS View Window Automotive Help
~D~
lfg xjso ms/div :::J l!!m:::J AJ20A
:::J fiic:::JJ x1 :::J c jott
:::J[oC:::Jl ott :::J
B -100-400V(x20J • Uoc:::JJx5 :::J oj~
ott ---3~
. Joc:::JJ ott :::J
V (x20)
A
12·-•
•••
•
.
.•
1 CJ.• •
Injector Current measured at the fuse box, sync probe on #2 injector control
wire to identify current ramps using the firing order.
•
••
•
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'
a' • • • • • • • • •
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---- ----1-------
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275
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300
325
350
375
400 m s
--'--············•··-···-···-···'··········
i
•
.,' -·············II.
•
~--- · ·········-~---··········-L .............. ! . . . . . . . . . . . . . . ! . . • . • . . . • . . . • . ! . . . . . . . . . . . . . . i . . . . . . . . . . . . . . ! . . . . . . . . . . . . . . J • • • • • • • • • • • • • • J ••••••••• • ••• • ~10
150
175
200
225
A = injector current (all) B = # 2 cyl injector volt age pattern
Firing order = 1-8-4-3·6-5-7·2
•
Il:J
W aiting lo
No Start, Engine Cranking. Each injector should be drawing less than [
1 amp of current. There is only 1 maybe 2 good injectors out of 8!
•
18
Faulty PCM Injector DrivePJ~
File Edit Settings View Window
Automotive Help
15J D~ ~ x r 2 0 ms/div 3 fH3 AL.200 mV
3 fOc3 x l
B J"i0 -ff --.....;;3;.; ; ,
200-- - 1 60---.; .. - . - -i- -- -- . .;. --- . -i------.\· - -- - - ~-- - . ---:- - -- - -.\- -- -- --:--. --- -:--'
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1 ···-----..
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80- -+------~------ ~ · -----!-------:--- -:-------:-------: ------:-------:--'
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19
m'7 ~
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Secondary Ignition vs. Injector Voltage Waveforms
http://www.youtube.com/watch?v=NXrd1fYwj1 o
Known good, snap throttle test.
Lean misfire, snap throttle test.
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20
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(i njector st uck clo s ed)
First look, it seems there is no difference. Zoomed in the
following two captures reveals the problem.
21
Stick 1ng Pintle Case Study ffi~
•
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PicoScope
Edit Settings View Window Automotive Help
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22
•
Stick 1ng Pintle Case Studl(OJ~
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icoScopc
Eclt Settings
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Automotive
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9.0 9.5 1 0.0 1 0.5 11 .0 11.5 12.0
A = Injector Voltage B = Injector Current
[injector stuck closed)
Jch e31 J Rising 3 1~·6_
7 ~l$mV
23
Injector Current Measured On The ~S'To@ '
Al I Injectors
•
'
"
..
"
VB Caddy, after tune-up this engine still
had a multiple cylinder misfire
"
•
3
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Awe A
0. 00
11ovie
c.....r
V6 Nissan, multi-cylinder misfire
1
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GM 3800 SFI during a no misfire condition
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GM 3800 SFI during misfire condition. This
ended up being an ECM driver problem. A new
ECM fixed this condition .
'
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mt
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Sticking Pintle, Single Cylinder
. I>
1
A
Thes e pictures show the time comparison of pintle opening/c losing of 5 known good injector s and 1
sticking injector. Notice that peak current and voltage is identical on the good and bad injectors
I
01
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LAB SCOPE
1s,nc
Lock
I
OH
I •• ? ls.ti l'Ufll
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IOff
I BI
#5 injector current and vo ltage waveform s
Balance test also revea led an injector mechanical problem
I H/ A
'
Siunal
Pi nut 1
Off
•
Patt.eJ'tVSweeul Sca l4!.
10 ...s
100 u
1•·rafoflc
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Bolh
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I 8
I
All other injectors looked like the above pictures
25
Injector Balance Testing
•
•
•
0
•
G
•
•
Used to test for injector flow
(mechanical) problems.
Requires the use of a special
timer tool that fires each injector
at the same interval, while
monitoring fuel psi drops.
Fuel system must hold rest
pressure to perform test
accurately.
Results may be misleading if test
is performed with the engine hot,
due to fuel boiling.
Do not fire an injector more than
once before cranking the engine
over. (hydro lock)
Maximum psi variation is 1.5 psi
from lowest to highest.
Fuel
TEST
1 st reading (initial pressure)
2nd reading (pressure after drop
Fuel rail
test port ~ c=~
Battery
e
Tester
http://www.youtube.com/watch?v=3CTuRW27n Q (Scan tool ba lance test)
http://www.youtube.com/watch ?v=Ss YM i3ylOT4
http://www.youtube .com/watch ?v= K7 STocr9FB I
26
0
G
No Injector Pulse, No Start
Problems
Section 19
No pulse no start good spark
•
•
Check injector feed voltage
Check for shorted injectors (only if the engine is an MPFI design that fires
injectors in groups)
http://www.youtube.com/watch?v=KF9vilxwJ Nc
http://www.youtube.com/watch?v=vmutNjx7QDY
•
0
G
•
•
Check crank and cam signals at the PCM
- It is possible to have good spark with no crank signal at the PCM ,
because the PCM does not control spark during cranking on some
systems
• Example - (early model) GM with a bad ignition module
Check for 5 volt reference to TPS or MAP
- If the PCM looses it's reference circuit nothing will work inside the
PCM. No communication , no MIL, no injector pulse etc.
- Refer to 5 volt reference testing.
Check for anti-theft system problems
2
ft>r
No Start From One Shorted In
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DK G AN
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3
~
No Pulse No Spark
• Check crank, cam signals
0
G
- Some cars need both crank and cam signals during cranking for
spark and injector pulse
- Some cars only need the crank signal during cranking for spark
and injector pulse
- Some cars have dual crank sensors
• One is used for piston position and rpm
• One is used for coil or cyl. l.D.
- Some cars have two separate crank sensors
• One being used for misfire monitoring and low speed timing
control , and the other for piston position , rpm and possibly cyl. l.D.
• Check 5 volt reference circuit
• Check for an antitheft system problem or aftermarket
alarm
4
m'7 ~
~
No pulse single cylinder misfire
•
•
•
•
•
•
0
G
•
Stuck shut or restricted injector
Bad injector
No power to injector
Open or shorted injector control wire
Open or shorted injector driver
Input sensor problem to the PCM (unlikely problem if only one cylinder is
affected)
Bad injector connector
SEE FUEL INJECTOR TESTING SECTION FOR PINPOINT TESTING OF
THE ABOVE PROBLEMS
5
Idle Speed Controls
0
G
Section 20
Idle Air Control Motors
•
IAC motor
Other common names:
1.
ABV - air bypass valve
2.
AIS - automatic id le speed
3.
AAC - auxiliary air control
Can be a stepper motor or PWM (pulse width
modulated) solenoid
0
G
Opens and closes an air bypass port around
the throttle plate to control idle speed
Idle air
control
~--=="¥-~actuator
~~~~Air bypass
Throttle plate is in a fixed position during idle
but not completely closed.
•
Airflow past the closed throttle plate
when all by-pass air is blocked is called
minimum airflow or minimum idle speed.
•
This MUST be maintained for proper id le
control
IAC position is learned by the computer and
changes over time due to carbon build-up
around the throttle body which restricts the
minimum airflow.
2
mV' r:
Idle Speed Control Motor
•
0
0
•
ISC motor (older design)
Is a reversible DC electric motor
with an integral nose switch
• Opens and closes the
throttle shaft and plate to
control idle speed
• Throttle plate is not in a fixed
position at idle
ETC (electronic throttle control)
systems
-
-
.....-:::::::::::::::::::::::::-
: : : : :--==::::::::::~
Idle speed
controller
(ISC)
I
Electronic
Throttle Body
Throttle angle and idle speed is
controlled using a reversible DC
electric motor
No separate idle speed control
device is used however the same
principles apply. Including
minimum airflow and its
importance in maintaining a
proper idle speed.
Reversible DC Electric Motor
3
m'7 ~
Inputs used to control idle speed
1.
2.
3.
0
G
4.
5.
6.
7.
8.
9.
~
TPS - when throttle is opened, PCM commands IAC to open.
(prevents deceleration stalling)
Idle contact switch (some systems) - must be closed at idle
for PCM to properly control idle speed. This input is also used
for acceleration enrichment.
ECT - cold engine fast idle speed
AC switch - idle load
Power Steering Pressure Switch - idle load
Park/Neutral - idle load
Battery voltage - idle load
RPM
Vehicle Speed Sensor - for repositioning IAC. With no VSS
input the idle speed control may be affected.
4
(Return to page 12)
TPS vs. IAC Counts
89
IdleAir Control
TPSensorV
0
cnt
Notice /AC count
increase with TPS
voltage increase
17
1.78
0.65
v 0.65
2188
G
When the PCM sees an increase in the TPS voltage it will react by opening up the IAC passage. This
will delay the RPM drop during deceleration which will prevent stalling. Particularly during rapid
deceleration.
A TPS that reads too high of voltage at idle may cause the PCM to think that your foot is on the gas
pedal. The PCM responds by opening up the IAC passage to prepare for deceleration. This will cause
the IAC counts to be very high, with a high idle speed complaint. You will also notice that the desired
idle speed will be much lower than what the actual RPM is, which will seem contradictory. {§ee "Self
~eroing TPS Case Study" pgs. 6-8)
5
m'7 ~
Self Zeroing TPS Case Study
•
1995 CHEVROLET
A/C
3.1 L V6 CHEVY SFI
A/T
** DATA ONLY. OK TO DR IVE. **
(NO CODES AVA ILABLE IN THIS MODE)
RPM_1846 02S(mV)_810 INTEGRATR_128
OPEN/CLSD LOOP_ CLSD IAC POSITION _ _ 38
FUEL TR IM
119 TR IM CELL_ _ _ _O
DESIRED IDLE
900 BASE PW(ms)
2.5
•
TPS(V)
•
•
•
•
•
•
•
•
•
•
•
•
COOLANT(°F)
219 MAT(°F)
92
0.98
MAP("Hg)
8.4 MAP(V)
28 .7 BARO(V)
4 .70
BARO("Hg)
EGR SOLENOID 1 OFF EGR SOLENO ID 2_0FF
EGR SOLENOID 3_0F F CCP DUTY CYCLE
0
0
KNOCK
NO KNOCK RETARD(~)
A/F RATIO
14.7 SPARK ADV(
25
14.0
BATTERY(V)
13.7 FUEL PUMP(V)
A/C PRESS(V)
0.34 A/C PRESS(PSI)
13
NO A/C CLUTCH
OFF
A/C REQUEST
T IME
1 :32 VEH SPEED(MPH)
0
P/N SW ITCH
P-N-- TCC BRAKE SW
CLSD
•
•
•
•
•
•
•
0
G
0.60 THROTTLE(0/o)_ _ _ 3
0
)
~
Customer complaint was a high idle
speed after replacing a nonadjustable TPS.
1.
If the Desired Idle is 900 and the
RPM is 1846, why isn't the
computer trying to reduce the idle
speed as indicated by the IAC
Position? Because the PCM
thinks your foot is on the gas
pedal.
2.
On this vehicle, is a closed throttle
of 3°/o normal? No
3.
When does the computer zero the
TPS? When the battery is
disconnected or every key
cycle. The computer looks at
the lowest TPS reading and
records it in memory as 0%
6
m ...,. ~
Self Zeroing TPS Case Study (c:n:7
•
•
•
•
•
•
•
0
G
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1995 CHEVROLET
A/C
3.1 L V6 CHEVY SFI
A/T
** DATA ONLY. OK TO DR IVE . **
(NO CODES AVA ILABLE IN THIS MODE)
RPM_1079 02S(mV)_ 142 INTEGRATR_ 126
OPEN/CLSD LOOP CLSD IAC POSITION
0
FUEL TR IM
129 TR IM CELL
16
DESIRED IDLE
825 BASE PW(ms)
2.7
TPS(V)
0.60 THROTTLE(0/o)
COOLANT(°F)
208 MAT(°F)
95
MAP("Hg)
9.5 MAP(V)
1.18
BARO("Hg)
28.4 BARO(V)
4.64
EGR SOLENOID 1 OF F EGR SOLENO ID 2 OFF
EGR SOLENOID 3 OFF CCP DUTY CYCLE
0
0
KNOCK
NO KNOCK RETARD(l1)
A/F RATIO
14.7 SPARK ADV( 0 )
19
BATTERY(V)
13.7 FUEL PUMP(V)
13.8
A/C PRESS(V)
0.34 A/C PRESS(PSI}
13
A/C REQUEST
NO A/C CLUTCH
OFF
0
T IME
0 :47 VEH SPEED(MPH)
P/N SW ITCH
P-N-- TCC BRAKE SW
CLSD
0
This capture was taken after
disconnecting the battery. This was
the only way to get the computer to
re-zero the new TPS. Most cars only
need the key to be cycled for this
process to take place.
So re-zeroing the TPS brought the
idle speed down by BOO RPM,
however there is still a problem with
this car.
The idle speed is still higher than
desired and the computer is now
out of correction based on the IA C
Position. The pintle is fully
extended, blocking all bypass air.
7
m'7 ~
Self Zeroing TPS Case Study (cont.)
•
•
•
•
•
•
•
0
G
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1995 CHEVROLET
A/C
3. 1L V6 CHEVY SFI
A/T
** DATA ON LY. OK TO DR IVE. **
(NO CODES AVA ILABLE IN THIS MODE)
RPM_750 02S(mV)_ 788INTEGRATR_ 130
OPE N/CLSD LOOP CLSD IAC POSITION
19
FUEL TRIM
123 TR IM CE LL
16
DESIRED IDLE
750 BASE PW(ms)
2.6
TPS(V)
0.60 THROTTLE(0/o)
~
This final capture was taken after
repairing an intake manifold
vacuum leak.
0
COOLANT(°F)
22 1 MAT(°F)
97
MAP("Hg)
10.3 MAP(V)
1.32
BARO("Hg)
28 .4 BARO(V)
4 .64
EGR SOLENOID 1- OFF EG R SOLE NOID 2- OFF
EGR SOLENOID 3 OF F CC P DU TY CYCLE
0
0
KNOC K
NO KNOCK RETAR D(r..)
A/F RATIO
14 .7 SPARK ADV( 0 )
25
BATTERY(V)
13.7 FUEL PUMP(V)
13.9
A/C PR ESS(V)
0.34 A/C PR ESS(PSI)
13
A/C REQUEST
NO A/C CLUTCH
OFF
0
T IME
3:50 VEH SPEE D(M PH)
P/N SW ITC H
P-N-- TCC BRAKE SW
CLSD
8
IAC Functional Testing
(solenoid or stepper type)
•
•
Cold engine start
- Listen for fast idle speed
Hot engine start
- Listen for engine flare up on every start
• A flare up shows you that the IAC motor is functional in both directions
•
0
G
•
Hot engine idle
- Increase and decrease accessory loads, put the transmission in gear,
turn steering wheel to the lock position
- Idle should remain stable, engine should not stall
Scan Tool testing
- Perform all the above tests while watching IAC motor position or 0/o
- Command IAC motor to open and close and listen for idle to change
9
Interpreting IAC Motor CoulW~
•
0
G
•
•
~
PCM adjusts the IAC pintle in short pulses, called steps or counts. Which
change the IAC pintle position.
- A "O" count= pintle is fully extended, blocking off all bypass air
- A "255 count" = pintle is fully retracted , allowing full bypass air
- PCM keeps track of the IAC pintle position by frequently re-orienting the IAC
pintle zero count. In other words, it winds the IAC motor to the fully closed
position then backs it out a predetermined number of counts.
• This may be done on every key cycle or only at a certain vehicle speeds
using the VSS input.
- Bypass air increases as counts increase.
• Cold engine, initial start-up, TPS off idle or with high accessory loads it is
normal to have high IAC counts.
• A hot engine at idle with no accessory loads the IAC position generally
ranges from 20-30 counts on a GM or Chrysler.
Higher than normal counts or duty cycle (solenoid type)
- Dirty throttle body or restricted IAC passages
- Engine running poorly (multi-cylinder misfire etc.)
- Vacuum leak on a MAF engine
- Sticking IAC motor, wiring problem to the IAC, or faulty PCM
- One of the inputs the PCM uses to control the IAC is f(;ulty causing the PCM to
command a higher IAC count 7see ''"SelfZeroing TPS asestuc[ij" pgs. 6:cD
Lower than normal counts or duty cycle (solenoid type)
- Vacuum leak on a MAP engine
- Misadjusted base idle screw (some fool turned the screw)
1o
- Sticking IAC motor
Minimum Idle Speed
0
G
•IAC design (stepper or solenoid type)
• Is the amount of air flow past the closed throttle plate when all
bypass air is blocked off
1. Is restored by cleaning the throttle body in most cases.
2. Becomes restricted by carbon deposits that form around the
throttle body and plate
• Complaints associated with a dirty throttle body are: deceleration
stalling, start-stall, stalls at stops, always restarts, will not stall if
one foot is kept on the gas. Check engine light on with Idle Speed
Control trouble codes.
• Should be cleaned with a small brush and carb cleaner for any of
the above complaints, before any further diagnosis is done on an
idle control system.
3. Some systems provide adjustment (factory set) with a base idle
stop screw.
• Should never need to be adjusted
• Misadjustment will cause incorrect IAC/ISC operation and incorrect
TPS idle voltage readings
11
Why does a dirty throttle body ruamse ~ ~ .D
stalling problems?
•
•
"Idle Loads" = anything that would add a "load" to the crankshaft and cause an
RPM drop. Examples: AC clutch on, alternator loads, automatic transmission
placed in gear, high power steering pressure, etc.
The PCM only allows a certain range for all idle load compensation .
Example 1: An IAC stepper can operate in 256 different positions however
within the programming the manufacture may only allow a range from 0 to 50
to control all warm engine idle loads. When the throttle body gets dirty, all of
the allotted idle counts will be "used up" just to keep the engine idling normally
without any idle loads. Once idle loads are added, there isn't enough
compensation left to properly control the idle speed. This will cause intermittent
stalling problems.
- Example 2 : In an ETC system the throttle plate can be controlled from 0 to
100°/o opening. However idle load compensation (when your foot is off the gas
pedal) is only given a 15-20°/o window of operation. Once the throttle plate gets
dirty, the throttle percentage needs to be higher just to compensate for the
carbon build up. This limits how much control the PCM will allow for idle loads.
This may cause intermittent stalling problems and idle speed control trouble
codes. (See "2006 Chevy ETC System Case Study" pages 13 and 14)
During cold fast idle or TPS reaction (See "TPS vs. /AC Counts'? the IAC motor
position or the throttle percentage will operate outside of the idle load compensation
range, so you will see higher percentage and "counts" during these times.
12
-
0
G
•
ffi~~
~~ .D
2006 Chevy ETC System Case Study
No accessory loads
RPM
0
4D
DESIRED IDLE
TPS[%)
DESIRED TP[%]
788
768
21
21
All accessory loads
RPM
DESIRED IDLE
TPS[%)
DESIRED TP[%]
771
768
25
26
Notice TPS% just to keep this engine idling with No accessory loads. This dirty throttle
plate has used up most of the allowable idle load compensation range.
13
ffi~ ~
~~ .D
2006 Chevy ETC System Case Study
No accessory loads
0
G
679
672
6
RPM
DESIREDIDLE
TPS[%]
DESIREDTP(%)
6
All accessory loads
RPM
DESIREDIDLE
TPS[%]
DESIREDTP[%]
772
768
14
14
Notice TPS% after cleaning. This greatly increased the systems idle load
compensation ability. No more stalling problems on this engine!
14
ffi ~
~ ~D
Scope Testing Stepper Type IAC l\ltotors
•
•
•
•
0
G
•
•
•
4-wire GM/Chrysler or 6-wire Nissan
Connect scope (+) lead to each of the IAC control wires individually
Connect scope(-) lead to a known good ground
For proper control testing of each wire, the IAC motor must be commanded to
extend and retract.
Perform one of the following to extend and retract the IAC motor:
1.
Scan tool bi-directional controls (all Chryslers)
2.
Cycle the key on and off
The PCM moves the IAC pintle in both directions to prepare for
start-up
3.
Engine idling, increase and decrease accessory loads
IAC command will change in response
4.
Engine idling, snap throttle
An increase in TPS voltage will change IAC command
All IAC control wires should show a clean square wave type pattern. Some
voltage spikes are acceptable. (See Chrysler 4- wire stepper example]
If all IAC control wires show good activity and the IAC motor doesn't respond
properly, suspect faulty IAC motor.
If any of the IAC control wires show a poor or no square wave pattern then
suspect wiring or PCM problem (see GM and Nissan case studies)
15
(Return)
4-Wire Stepper Motor
PCM
Coil A
I
I
I
I
I
I
I
11
I
0
+
G
Coil B
F-
I
I
I
I
I
I
I
I
16
Chrysler 4-Wire Stepper Type IAC wa'1Jtf8rm~ ~ o
(Known Good)
50
10
40
20
~~~~M~:: :
LJUlJlJ J JlJl
10
t--~"""•:· :
IAC Plugged In
: _J:m~~~~~~~~u uu
10
-5
0
0
•
Testing performed with a scan tool
in bi-directional control mode with
the KOEO
Driver
7.G
7.0
7.2
7.•
B = 1 2 Drive r C = •3 Orlve r 0 • #4 Driver
durinq KOEO t eat (IAC extendlrc tr•ctl tAC pluqqcd in
11
40
2
10
·20
0
·30
· 10
40
20
•mi~::
50
ru:o
30
·1 0
10
20
0
38
· 10
· 40
·20
~o
· 30
~~~~~~~~~n
40
20
IAC Unplugged
~
0
-10
10
Voltage Spikes Indicate Current
Flow
n
:: ·::1r1~~~~~~~~~u u
50
10
4.4
4 .6
4 . 11
5.0
5.4
5.G
0 • • 2 Driver C = # 3 Driver
!i.2
5.8
A = #1 Orivcr
0 = #4 Oriver
'fn ken during KOEO \c t.it (lAC extend/retract) IAC n1ulor unplugged
6.0
6.2
6. 4 9
17
m ...,. ~
V
(Return)
I
GM Stepper IAC Case Study
Coil A
Coil A
Coil B
---
Coil B
I
I
14
I
__.,.._
0
I
Scope aliasing of a rapidly
pulsing square wave pattern
0.54U
0
13.43UDC
G
Customer complaint was a constant high idle speed.
Visual testing revealed that the IAC pintle would retract (increases idle) but would not
extend (decreases idle). Replacing the IAC motor did not fix this condition. The IAC
driver in the PCM was bad for coil A.
The capture above was taken while cycling the key on and off and testing each of the
four control wires one at a time. Note the problems on coil A not reaching full battery
voltage and full ground at different times. A zoomed in picture of coil A showed poor
square wave patterns.
18
6-Wire Stepper Motor
PCM
IAC
--------------~,,
~
~
H
~
0
G
>-
(
(
~
>
>
aa
B+
B+
aa
~,,
~,,
r
>>-
Stepper Motor--------
'''
Stator
'
'
'''
''
''
'''
'
'
'---------- ---------------''
http://www.youtube.com/watch?v=Wt zTJWbDzs
~,,
Nissan 6-wire Stepper IAC
19
2001 Nissan Maxima IAC Motor CascDJS'iidy ~ ~ .o
(Return)
4
6 ~~_r:~ -~-~~P.P~-~ -~YP.~--~AG__(~ .P.~~~r,f~~~~-~.~~--4__~Gr~--~-~~~r~!!~~- g-~~~-r:i-~~l: .Ih_i_~----·v
picture shows the:4 IAC to PCM control wires measured:at the P.CM connector. :
I
30
I
.•'r- ----------- ..•T·-----------1-• - -'
••
•
•
•
•
20
-10
0
G
-20
-30
-40
-50
••
••
~ - - - · - - • - -- • • ; . · - -- -- - HH< I
•
•
•
••
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- - - - -- • - -- - -i• - -- -- -- •••
10
0
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'
'
--,------------,-------------,-------------r------------r------------r------------,------------1
I
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t
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i2 coils pperati~g prop~rly. Th~
I
'
i
--1------------,-------------,-------------r------------r------------r------------r-----------·1
:
!P CM isl pulsinQ the co Is on
__:____________:a nd _off_:to_gr_o uhd_._____________ __ ____________ _____
I
50
40
I
•
•
•
50i,___ _.___
30
2 coils not operating properly. The
40; ------------:-------·r·----- ··-·r·-------- PCM is not pulsing the coils on and ;o
.................. .&...........
.
.
off to ground. There is some activity, 10
..... ....................................
·
·
:
i
but the circuit must get pulled all the
o: ____________ :________
_j_ __ _______ __ j___ _ ___ way to ground for the coils to
10
2'
.
:•
:•
energize. With this circuit being
10:. ------------ :___ _______ __ ; ____________ ;______ ----~.---------- tested directly at the PCM connector !o
i
i
~
:
i
there can be only one problem =
•
•
3~
I
I
I
I
o~ ------------ 1 --------~~:~-·~~)~'.~-~ - ; ------------ ~---------- Bad PCM Transistor Drivers
20
10
0
-10
10
-20
-1o~ ------------~ ------------:------------:-------------· -------------·-------------'-------------~ ------------~ ------------~ ------------·O
-30
..
I
'
''
I
'
''
I
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0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
All 4 coils should be
A= ECM PIN 17 gry/blu 8 = ECM PIN 7 yel/blk C = ECM PIN 8 yel
energized during t is
0 = ECM PIN 6 wht}ppl
condition
NO IAC flare up. OTC P0505
Taken during initial key on
4.5
5.0 s
20
m'7 ~
2-wire Solenoid Type IAC
•
•
•
0
G
•
~
This is a spring loaded closed solenoid
valve.
Idle Air Conlrol Molor
Amount of valve opening is dependent on
the magnetic field strength of the solenoid
coil.
Magnetic field strength is controlled by
varying the current flow through the
solenoid coil using a variable on time.
(pulse width modulation or duty cycle)
- The longer the duty cycle, the higher
the magnetic field strength , the more
the valve opens, the higher the idle
speed (see Ford Explorer example) http://www.youtube.com/watch?v=WoFt3uzQd44
Ford IAC valve position vs. duty cycle 0/o
- 20°/o duty cycle command = valve is
fully closed
- 50-60°/o duty cycle command = valve
fully open
- Typical idle duty cycle command =
30-40°/o with no accessory loads, in
park
21
Scope Testing Solenoid Type IAC ltLTh8rs ~
0
G
•
2-wire type
•
•
•
Connect scope (+) lead to the IAC control wire
Connect scope (-) lead to a known good ground
For proper control testing, the IAC motor must be commanded to extend and retract.
Perform one of the following to extend and retract the IAC motor:
1.
Scan tool bi-directional controls
2.
Cycle the key on and off
The PCM moves the IAC pintle to prepare for start-up
3.
Engine idling, increase and decrease accessory loads
IAC command will change in response
4.
Engine idling, snap th rottle
An increase in TPS voltage will change IAC command
The IAC control wire should show a pulsing on-off signal with lows near zero volts and
highs near battery volts. Some voltage spikes are acceptable. See examples below.
If the IAC control wire shows good activity and the IAC motor doesn't respond properly,
suspect faulty IAC motor.
If the IAC control w ire shows poor control suspect wiring or PCM problem . While also
keeping in mind an open in the IAC coil winding would show no control.
•
•
•
~
..
j
.
1 _
11;-
.
lll
10
0
_,
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10 .
l
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....
10
•
1 191 Fol'.d Rrobe ... "
...
.
99 · Honda c·vic
s
1. I 6
. ..I
"
'"
'
or~ E! .01
Ford Explorer 2-Wire IAC SoletRtiiU
(Known Good)
20
16
-·-
180•
•
160
h-
~
12
140 . . . .
8
120
.
0
80''
6 0~
.:
.:
.:
.
•
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•
h . ' ;.;.;... ~ .. ~ ;. j.;,.; •• ·,;.; •• ~-. ;.;..: •• ~ .. ~ . "i,:.; •• ~ •• ~
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1.
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.:
.
. .. ' .. . .. . . . . .. . . . . . ,••• . . . . .. . ,. . .. . .. . ,..
.•
IAC Power Feed
,
•
. . .. ' . . . . '•, . .. . .. .
.
•
100 . . .. .
0
.:
.:
································~······-······ ~---·········-~·-···········...-·············~·············~··············
...
IAC Control
•
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.. . - ;' . .. . .. .
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---:--------------~-------------~
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-------· -----------. -"' ----------. --...
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• •
·8
-12
-16
'
-20
-20'
0
2
100mv = 1 amp
4
6
8
10
12
14
'
.................................
15
'
'
16
18
20 ms
ch k Frequency(l:Hz)
ch k Duty cycl e lowl"!
1.408
38.49
A = IAC Control B = IAC Feed C = IAC Current
_ _ _ _ _ _ _ _ _H
:.:.:.
ot:.:E
: :n::.:gine, No Acce ssory Loads
23
Ford Explorer 2-Wire IAC SolmoTtt
(Known Good)
v
20
16
mV
v
180·' -----. -------~ -. ----------- ~ . ----. -------..' ---------. ---..' --------. ----... ------. -----..' ------. ------··-' ------. ------.- . -----------.,.' ------------..'
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•
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-20
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-- ...... -... _;_ .... -. -.... . ···----------~-------------~------------- ~ -------------~---······-····:·····-------- ~ -----·······-~-----·······- ~4
•
•
.
'
'
~
•
0
'
~8
•
Notice the increase in duty cycle and current flow as
o~ -- . -- --. --... : .. -- --. accessory loads are increased (50°/o duty cycle)
•
•
-20~
'
-~
.
. -- . -- -----~• -. -- -- . -- --- -~12
•
'
.
'
'
14
16
18
20 ms
. -. -. --. --. -. ! .. - . - - - - .. - .. ! . - . - - . - - . - ... ~ - . - - - - .. - . - . - ~ - - - - - .. - . - . - - : - .. - . - . - - . - - . -·. - - . - . - - - - - . - .·- .. - . - - - - .. - . -·- - - . - - . - .. - ...'. - . - - . - - . - ... - ~16
2
4
6
8
10
12
ch A: Frequency(kHz)
1.021
ch A: Duty cycle low[%)
50.50
A = IAC Control B = IAC Feed C = IAC Current
Hot Engine, All Accessory Loads On
24
m ...,. ~
3-Wire Solenoid Type IAC
Rotary Three-Wire Idle
Bypass Valve
30°10
0
G
v
~
•
Contains a rotating plate that
controls the amount of bypass
•
air.
•
Direction that the plate rotates
depends on which coil has a
stronger magnetic field.
Coil magnetic field is controlled
by varying the current flow
through each coil.
•
-
Pulse-Width Modulated
70°10
http://www.youtube.com/watch?v=sg3J4ibMkWc
http://www.youtube.com/watch?v=9c1YSic7ejs1
This is done by a duty cycle
control from 0 to 100°/o
- The sum of the duty cycle 0/o of
both coils is equal to 100°/o
under all conditions
(see "Toyota 3-wire Solenoid Type
/AC Waveform")
25
Toyota 3-Wire Solenoid Type IAC Wa[Q)Jwm @ ~ o
(Known Good)
-
-
-
-
,_
-
~
,_
nn
L.
74.99°/o on time
20
244 HZ
LJLJ
16
8
nnn
0
u u
12
•4
· 15
0
23.53°/o on time
'-
'---
-10
'---
~
-5
0
.._
L..
15
10
5
L-
L-
-16
· 20
30
25
20
-
- 12
JS ms
nnn
CD
12
8
No
27.45°/o on time
20
244 HZ 1 6
12
= = --
..__
.....
-
-
~
J-
8
LJ
LJ
nn
-
-
" A ccessory
o
Loads On
70.96°/o on time
•
-12
LJ LJ
u
-10
u
10
15
zu
- 16
25
In these captures the " ON" time is low and the " OFF" ti me is high
JU
26
Other Idle Controls
•
0
G
Components
1. Mechanical cold fast
idle valve (coolant
temperature
controlled)
2. Fast Idle Control
Device (F.l.C.D.)
3. Idle-up Solenoid
27
Other Idle Controls
•
Components
1.
2.
Idle Air Adjusting Unit
Fast Idle Control Device
(F.l.C.D.)
Auxiliary Air Control Valve
(A.A.C.)
Air Regulator Valve or
Auxiliary Air Valve (A.A .V.)
3.
4.
0
0
Heater
I
• u
I
I
Air Flow Blocked
Engine Warm
Electrical
Connection
Air Bypass
Valve
The main point in this illustration is to show how
many variations there are w hen it comes to idle
speed controls. You must do research on the
system you are working on before attempting a
diagnosis. There are just so many different
variations from year to year and manufacturer to
manufacturer.
28
m'7~
Typical Early Honda Idle ControlS
Can be adjusted
instead of cleaning the
throttle body.
Adjusting it in too far
will cause the same
symptoms as a dirty
throttle body.
Adjusting it out too far
will cause higher than
normal idle speeds and
IAC position problems
0
~
Just showing another
variation
~ Minimum Air
Flow Bypass Screw
To Engine
Air Inlet
G
Thermal Wax
:;:::...J Air Bypass
AIS Motor
..--- Coolant
.....____ Passages
Typical 2-wire solenoid type IAC with a
variable duty cycle
Mechanical Cold Fast Idle Valve Should
be closed below 100 degrees coolant
temp.
29
Ignition System lneuts
0
G
Section 21
Variable Reluctance Sensors (Vf&f
•
0
G
Description and Operation
2 wire sensor that's makes its own voltage using the principles of motion, a
magnet and a conductor. (see figure 1)
- Signal output is an AC voltage that increases in amplitude and frequency as RPM
increases (see figure 2)
Sensor to reluctor air gap is critical (see figures ~ and ;JQ, 1£ and 4b)
• Too wide= weak signal
• Too close= reluctor may hit the sensor
Signal circuit is usually shielded (see figure 12)
- There are major differences in electronic circuitry within a module using an analog to
digital (AD) converter. This will affect how the scope (DSO) gets connected to the
sensor for proper waveform interpretation.
• Some will use a bias voltage on sensor(+) or sensor(-). While others use no
bias voltage at all. (see figures Q_and §)
• Some sensors will show a waveform on only the (+)wire. With this type the (-)
wire is either equal to battery negative or will have a bias voltage on it from
around 1 to 5 volts DC. (see figures §. and §)
• Some sensors will show a waveform on the~+) and on the(-) wires. This type of
sensor has what's called a "floating ground '. (see figures Z and fl)
- The AD converter will cause a current draw on the VRS. This is a normal condition
and means that the amplitude of the signal will be lower with the sensor plugged in.
(see figure 9)
The AD converter requires an input minimum of around 500mv (see figure 10)
2
(Return)
VRS Waveform Overview
+
-.. .. ......
....
.. .. . .. .. . .. .. . .. . ... .. .. .. •'
--
MAXIMUM
POSITIVE
SWING
+
ov ! - ' - - - - - - - - - - -
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.
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SWINGS
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Figure 1
................ .. ..... .
..... ..........................
......................
. . ,,.
.. .. ... ... .......
. ......
•
+
OVI--_.__ _ __,,__- - - - , -
MAXIMUM
NEGATIVE
SWI N G
3
(Return to page 2)
VRS Signal At Different Speeds
(Return to page 15)
v
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20
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............ ......•
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-12
-16
20
0
-8
8
·20
95 97 99 102 105 ms
CKP C = Coil Current D = #1 cyl
Idle
1.G!
' -r'\-,-.' ' • ••
,-,-1
'
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•
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v
.... ,.,.."'.., .... ,... .,..•v
0
1.6'
·20
1J
492 495 498 501 ms
CKP C = Coil Current D = 11 cyl.
Cranking
Figure 2
I
'
,....,. '.,. ,. ,.,....,..,.,
'
I
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1. ..... . . . . . . . . . . . . . . ~ .. .
50
I
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40
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• • • •
2•lf..•••••••
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• • • •' • • • • • • •
. ...
·12
-16
1.6'
ll
-20
95 97 99 102 105 ms
CKP C = Coil Current D = #1 cyl
@2000 RPM
1
4
WSS AIR GAP PROBLEM
(Return)
• ft' x
•
v
2.~ ···························~··············································································~··············-··············:···············:··
.
.
.
.
Rust on the hub caused the speed sensor to lift
off of its mounting point, increasing the air gap.
....
....
....
....
.....................;..................................................................; .........................;............;..
.....
.....
.....
.....
.
.
.
.
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0
.
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.
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O.•··········· ················~············ ····························· ····························· ········~···················· ··········:···············:··
1
uu1Jlftl1~lll
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.
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...............................1
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.
.
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·!."···························~··············································································:··············-··············:···············:··
...
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.u.• ···························:··············································································~·······························:···············:··
.
.
.
·2.~···························:..............................................................................:...............................:...............:.. s
..
a
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Figure 3a
~
u
11
u
u
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u
Ji : Rf V.'SSlbtfuo: de1t1i11ghub)
5
WSS AIR GAP PROBLEM
(Return)
• v
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....
....
....
.
.
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..
l.&···························i··············································································~······························i···············i··
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ii
12
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M
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Figure 3b
A" Rf WSSI* •deoung l' b)
6
VRS Reluctor/Air Gap Problem~
(Return)
0
8
The reluctor shift here
(smaller air gap)= an
increased amplitude here
0
------
-L
Figure 4a
7
(Return to page 2!
VRS Air Gap Problems
Caused by a the misuse of a pry bar
when replacing a ball joint.
0
0
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Figure 4b
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- t d.
8
VRS with 1 volt DC BiaSOJJ~
(Return to page 2)
--------.---------------.-------.--.-.-.--.l
.
(Return to page 15~
4,_______ _ '
..
.
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Blue = VRS (·)
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.
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. DC bia$.
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··········r·············-~---········································-~-
111\1
.-
,. .
?·---
Red =VRS (+)
Dual Trace
..
.. with scope (-)
'----1--------------~ connected to
-. --. -~-. -- ----. --.. -2
BAT (·)
-- - -- - -- -- - -- - ~ - - -- - -- -- - -- - - ~- -- - -- - -- -- - -- ~2
-----·:··----·--·-··-;·-·-----·-··--;------··--·--- ~
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.
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i
111
Scope(-)
connected to
BAT(-)
.:2
'
----- ---- --- --~- ............ -~ .............. ; .............. : .............. ; .............. ; .............. ; .............. ;_ ............. ;_ ............. .:.....
".............. ·:· ... .
•
·····-:···············i···············:················.
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.
. _. __ . __ . _.;. _. __ . __ . .N o~ice .the .DQ. bjas. is ._-~
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•
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·····························~···········-·
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Scope(-)
connected to
sensor( -)
. ; .. --.. ----. -.. -: .. -...... -.. -..:... -.. -.. -.. -.. : .•-.• -.• -.• -.•. :.2
I
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Figure 5
9
(Return)
VRS with no bias
v
..
..
..
.
..
v
.
..
.
a~--------------~--------------~--------------·--------------y--------------y--------------y--------------·--------------~--------------~--------------~
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'
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'
and so does the coil prim ary circuits. This is a normal condition when viewing these signals with the
'
'
-------- 6
causi~g signal voltage rise
---·--------------·--------------·--------------·--------------?·-------------~--------------~-------------- ~
CKP (-)
_,..t1"1
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scope connected to battery ground . If the scope was connected to sensor ground (CKP -) while
watching the sensor signal (CKP+ ), you would not see this noise.
:
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L------ --------L--------------L--------------l--------------l--------------l--------------l--------------!--------------J-------------- J-- ------------ L6
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0. 2
0.3
0.4
0.5
0.6
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0.7
0.8
0.9
1.0 s
A = CKP (+)
8 = CKP (-) . Cranking with sensor plugged in.
Amplitude is lower in thi s pie. due to slow cr anking. No bias voltage
on this system.
Figure 6
10
mV'~
@
Connecting to a VRS with a floating ground.
(Return to page 2)
(Return to page 15)
1\ (\r
.1--------111•
-~f IJoO
+ .__I- -
DSO connected this way will cut the
amplitude in half.
PCM
_ _ _ _ CKP (+)
0
0
[•
_ _ _ _ CKP (-)
+
lJoO
,
\ f I
J
Figure 7
DSO connected this
way will show fu ll
amplitude.
11
VRS with a ''Floating Ground''
(Return to page 2)
Dual trace with scope(-) leads on ground
(Return to page
15)
-:' ..............
- - -.~ .............................
-- . --- - '- - :'- :' ............................
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Single trace with scope(-) lead on CKP (-)
----------..---I
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O
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12
VRS unplugged/plugged in compari~n~
(Return to page 2)
(Return to page 15)
x=4831 mV,o=-4703mV,xo=-9534mV
v
v
10~------r------·------·------.------- .. ------.,------.,------i------.,------.,
•
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x=411 OmV,o=-3475mV,xo=-7585mV
107······r------9··--·-9··--·-9·-----,------,------,------~------~------~
I
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. testing this type of crank sensor during a no spark condition. You must leave the sensor plugged in, for an
.---
accurate measurement of amplitude. If you unplug the sensor to measure its signal, a bad sensor can look
good and cause you to misdiagnose the problem.
.. . . ...•
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300
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400
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A= CKP Signal with sensor unplugged from the ICM. (cranking)
Figure 9
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300
350
400
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750
A = CKP Signal with sensor plugged in. (cranking)
13
AC Signal Amplitude vs. Digital ConvemfJR
(Return to page 2)
v
(Return to page 15)
x=1327mV,o=659mV.xo=-668mV
.
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-500
Figure 10
-250
0
750
1250
250
500
1000
A = Pick-up Coil Signal B = Reference Pul se
Picture shows the minimum input needed to trigger the AD coverter
1500
1750
ms
14
Scope testing a VRS
•
•
•
•
0
G
•
•
Do not unplug the sensor (see figure 9)
Always connect to the harness side of the sensor connector whenever possible
Connect DSO (+)lead to sensor(+)
Connect DSO (-)lead to sensor(-) or battery ground .
When to connect to sensor (-)
1. To see full amplitude on a sensor with a floating ground. (see figures Z and §)
2. When you want a cleaner signal
3. Single trace testing only, do not use sensor (-) when measuring more than
one signal at a time. The scope shares grounds between all channels.
4. When you have a no start and you want to see full signal amplitude
regardless of which type of circuit design the computer uses.
When to connect to battery ground
1. When performing multiple trace testing (multiple signals at the same time)
2. When you just need a signal and do not care about amplitude
3. If you want to view the bias voltage levels on the circuit (see figure S)
Look for proper amplitude, frequency and waveform
1. Amplitude must be a minimum of +/- 500mv for the AD converter to "see" the
signal (see figure f O)
2. Amplitude and frequency will increase with speed (see figure 2)
3. Waveform will be unique to the application
May use an AC voltmeter using the same connections as the DSO .
This meter will only show an average voltage so the signal will be lower in
amplitude than if measuring with a DSO.
15
VRS No Signal Testing
•
•
•
0
G
Possible problems vary depending on testing location and scope connections.
1.
Bad Sensor
2.
Open or short to ground in the sensor wiring between sensor and
module
3.
Broken or missing reluctor or no motion
4. Air gap problems
If possible do a visual inspection of the reluctor and the air gap .
Before condemning sensor you must verify there are no opens or shorts in the
wiring to the sensor. Verify signal circuit integrity.
1.
Measure bias voltage on sensor (+) and sensor (-) with the sensor
unplugged and plugged in to verify circuit integrity. Wig~le the wirin9 and
connectors and look for a bias voltage change, this will indicate a wiring
problem. http://www.youtube.com/watch?v=bPdPhGcZOeO (ABS wss Testing)
2.
Perform a bypass test
Test light to BAT(+) and touch on and off the signal wire (be the sensor)
If you get a response this confirms signal circuit integrity (no opens or
shorts in signal wire) (see figures n12.. and1~)
3.
Other Tests:
•
Measure resistance of the sensor using an ohmmeter (remember that
this only checks the winding and not the motion or the magnetic field
strength)
•
Measure sensor(+) and sensor(-) wires for opens and shorts between
sensor and module.
16
m'7~
EARLY GM DI IGNITION VRS BYPASS TEST
(Return)
~
PCM
Touch on/off here
with test light
BARO
MAP
PICKUP
COIL
ECT
REFERENCE
BATTERY
0
.
"
EST
E
s
T
IGNITION
COIL
I
I
G
AD
Conve1ter
I
GAO
-
5 V BYPASS
•
~
Coil should spark during test
http://www. youtu be. com/watch ?v=fra26yvvc-I
VRS Bypass Testing
http://www.youtube.com/watch?v=mxPdxGqRWvq
GM Bypass Ignition System Operation
Figure 11
17
(Return)
TES~'V ~
EARLY GM El IGNITION VRS BYPASS
Touch on/off here
with test light
~
I
~REO
--
•
I
C:AANK
SE
~'T
C: 1 00
D•
PPL
NOA
BLK~HT
PP L _..., HT
T AN-BL lC
WHT
0
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.
o es N O D '-«1 e
....:
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c:
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Coils should spark at random during test
Figure 12
18
mV' r:
(Return)
EARLY TOYOTA VRS BYPASS TEST
Touch on/off here
with test light
DISTRIBUTOR
0
©
8Lk
0
-(';,
I
I
COil 1I
To ECU
-
:r
•
lgnitor Powe r
Feed
Coil should spark during test
Figure 13
19
Hall Effect Sensors
•
•
0
G
Description and Operation
- 3 or 4 wire sensor that needs an external power and ground to work (may share power
and ground with other sensors)
• Some newer systems are using 2 wire hall effects (wheel speed sensors)
- The main component inside of a hall effect is a transistor. The transistor turns on and off
to make a square wave signal.
- Signal output is digital (square wave), amplitude is constant only frequency increases with
speed
- Signal circuit is either a pull-up or pull-down design (see figures 11 4 and 15)
- Some are adjustable (for air gap only in most cases)
- Signal voltage can ra nge between 5 and 12 volts
Testing Hall Effects
- Connect DSO (-) lead to BAT (-) and the ( +) lead to each of the hall wires individually.
- Check signal (two signals on a 4 w ire) KOEC (cranking) or KOER (running)= look for
proper amplitude and waveform (must know description and operation of the system)
• If signal is out of range or no signal appears, check power and ground to the sensor
KOEC or KOER
- Power feed to the hall sensor can be anywhere from 5 to 12 volts
» For systems using the 5v reference circuit to power the hall sensors, no
power (reference) can be caused by a shorted circuit. (see "The 5 Volt
reference circuit" for further testing)
- Ground circuit must be .1 volt (100 mv) or less
• Signal out of ra nge with good external power and grou nd
- Bad sensor, open or shorted signal wire , bad module or PCM, mechanical
failure
» Perform hall effect bypass test
» Follow Pull-up and Pull-down flow charts . Troubleshooting hall effect
circuits is identical to mechanical switch input circuits with the exception
of an external power and ground that must be verified.
20
- YOU MUST KNOW IF T HE CIRC UIT IS PULL-U P O R PU LL-DOWN!!!!
Pull Down Testing
Signal voltage measured
at the sensor is fixed low
Disconnect sensor
•
•
Signal voltage
goes high
Signal voltage
stays low
0
G
Bad Sensor
Measure signal
at the PCM
Perform bypass
test to confirm
•
•
Signal high = Open
In the signal
wire
Short to ground
In the signal wire
Signal low
PCM Problem
21
Pull Down Testing
Signal voltage measured at
the sensor is fixed high
I
•
Check sensor power supply .
Should read between 5 and 12v.
Normal supply voltage
I
•
-.
No supply voltage
0
G
Check sensor ground.
I
•
Check supply circuit for opens and shorts.
Remember other sensors may share
this same power supply.
100 mv or less
More than 100 mv
Faulty sensor or no
mechanical movement
Repair ground
http://www.youtube.com/watch?v=xwh3XM1 Nl4~
http://www.youtube.com/watch ?v=yp kK6 U8a64J
http://www.you tube. com/watch ?v=irHVj FTq4 LE
22
Pull Up Testing
Signal voltage measured
at the switch is fixed low
Check for mechanical {movement)
problems
I
0
Check switch power and ground
G
;r
.
Check signal wire for short to ground
•
•
Perform a bypass test
Use an ohmmeter
http ://www. youtu be.com/watch ?v= IzZN IPosGSY
http ://www. youtu be.com/watch ?v=OxP4 IMCd 06w
23
Pull-up Testing
'
/
Signal voltage measured
at the switch
is fixed high
"
'
/
0
Check for mechanical
problems
G
"
'
/
If none found then replace
the switch
Perform a bypass test to confirm
"
24
Pull-up Testing
OTC set for a pull-up switch input.
Switch tests good when measuring signal voltage at the switch
Check signal voltage
at the PCM
I
•
•
Signal is also good at
the PCM
Signal is low all the time
0
G
There is an open in
the signal wire between
sensor and computer
Check for poor PCM
Male to female
Terminal contact
I
•
If good, suspect
Faulty PCM
•
•
Check PCM powers
And grounds
before replacing
25
Hall effect bypass test
• Pull down design
• Disconnect sensor, connect test light to BAT (-)
- KOEO touch test light on and off to the signal wire
- Module or PCM should respond (see figure 14)
• Pull up design
0
G
• Disconnect sensor, connect test light to BAT ( +)
- KOEO touch test light on and off to the signal wire
- Module or PCM should respond (see figure 15)
NOTE: Module or PCM should respond by providing spark to ignition coil (some
systems need more than one signal at a time for spark control so you may not
get the response you're looking for)
• What response are you looking for if you cannot force the coil to spark?
- Injector pulse
- Scan data PIO changes: RPM , CRANK or CAM (see figure 16)
- Watch instrument cluster tachometer
• A bypass test can be done on ANY hall effect, not just on the ignition
system
26
Pull-Down Hall Effect By-Pass
(Return to page 20)
(Return to page 26)
Disconnect Hall sensor. Connect test
I'1g ht to ground and touch test light
on/off here.
PCM
5-12 Volt Feed
Signal
•
Hall effect
0
G
5-12 Volt Ref
•
Current ~mlting tesistor
~
Power
IC
Voltage
sensing
circuit
Ground
-Figure 14
27
Pull-Up Hall Effect By-Pass TelQJ'7 ~
~
(Return to page 20)
(Return to page 26)
PCM
Disconnect Hall sensor. Connect test
light to power and touch test light on/off
here.
Hall effect
0
n:
•
s .12 Volt Feed
Signal
1
Power
IC 1---.--1o----------"
G
Volta~e
StH ISlllY
circuit
Ground
,
Current Linliting
Resistor
-Figure 15
28
(Return to page 26)
0
0
•
1997 DODGE CAR JA
•
2.4L L4 MPI
•
CHRY ENG
•
NO CODES PRESENT
Scan Data Cam/Crank PIDs
AIT
AIC
•
23 RPM _
224 TPS(V)_ 3.77 INJ(ms)_O.O
•
IGN CYCLES 1
•
IGN CYCLES 3
0 OPENICLSD LOOP _OPEN
•
CRANK SENSOR
YES CAM SENSOR
•
CURRENT SYNC
OK DIS SGNL_ CAM&CRANK
•
MAP SNSR(V)
•
BARO PRES("Hg)_29.0 MIN TPS(V)
•
TPS(V)
•
COOLANT(V)
•
IAT(V)
Figure 16
255 IGN CYCLES 2
0
4.5 MAN VAC("Hg)
YES
0.0
0.78
3.77 THROTTLE(0/o)
84
1.5 COOLANT(°F)
113
2.19 IAT(°F)
90
•
UPSTRM 02S(V)_0.47 UPSTRM EXH_CENTER
•
DWNSTR M 02S(V)_ 0. 47 VEH SPEED(MPH)
•
ST ADAP( 0/o) _ _o.o LT ADAP( 01o) _ _o.o
•
SPARK ADV( 0 BTC)_
•
KNOCK SNSR(V)_0. 8 EGR SOLENO ID_BLOCK
•
RETARD CYL #1 _ _
0 RETARD CYL #2 _ _
0
•
RETARD CYL #3
0 RETARD CYL #4
0
•
PRGE DUTY CYC( 0/o)- 0 PWR STEER SW -
•
TARGET IAC
•
ENGINE RPM._
•
AU TO SHUTDOWN
•
FUEL ALLOWED
•
MALFUNCTION LMP OFF CALC LOAD VALUE
9 LIMP-IN
50 IAC (STEPS)
_
O
NONE
OPEN
50
224 DES IDLE RPM _ _ 792
ON FUEL PUMP RL Y_ _ ON
YES FUEL LEVEL(V)_ 1.95
4
29
Optical Distributors
•
•
•
0
G
•
Optical pick-up (see figures 17, ~ and 19)
Typically a 4 wire sensor (power, ground, and 2 separate signal wires)
• The power and ground can be shared with other sensors
• Signal output is digital, usually one high and one low frequency
signal
- Signal circuit is usually a pull-down design.
Testing optical pick-ups
- Refer to hall effect testing (use identical procedures)
Testing optical and hall effect sensors with a digital voltmeter
- You will not be able to see the actual min-max voltage level of a digital
signal due to the averaging of the voltmeter
- You will not be able to see actual waveform integrity
• You can bump start the engine to see min-max voltage
• You can use the average reading of the signal with engine running
or cranking to at least tell you that a signal is present
30
Optical Distributor
(Return)
LED
92Vtot•v- FROM PCM
VOLTAGE REOUlATOR
-.
LOW DATA
RATE SLOTS
(6 TOTAL)
DIST. SHAFT
/
LED
f
c
'
HIGH DATA RATE
SLOTS (360 TOTAL)
PHOTO·
DIODE
DISC
+
G
l:::::=fd
I
PHOTO
CELL
0
DISC
INTEGRATED
SENSING CIRCUIT
PCM
--
DISTRIBUTOR
SHAFT
RESISTOR A
sv
POINT B
VOLTAGE
SENSING
CIRCUIT
-.
VOi.TAGE NEAR ZERO WITH UGHT HITTING PHOTO CELL
Figure 17
31
v
Chrysler PCM 9 Volt Regulator Probl~
(8eturn)
16
!llllllU!lllUl!lllllUIHlllUll
'F
v
s
PCM 9 Volt Supply
10
UY UVU llUllINYUij5\l\IO\NUIJU ~~YUI U~U YU
10
,..
I"
8
-4
6
-o
4
- 12
2
16
0
-20
-2
0
v
-
18
v
16
"" ""
~
...
,..
,.,,
Sensor Ground
,,,.
~
8
.. "•• 'l., .,..,, t •"YO
~
""
.... .,,.
.
~
.....
..
("
-2
_..,
High data rate slgnal
._
6
~
'-
,.
.,
•
l..A ll.J lU ILJ l J LJ I .
Low data rate signal
2
ti
0
8
-2
J.,
The oscillations in the 9v supply (from a bad computer) was ca using the
LEDs to oscillate creating noise in the signal wires. Notice how clean the
signal is with a good 9v supply.
&
v
12
6
..
4
10
4
2
8
o.,..,, •tP p .....,...... ' ....... ,.,,.,,,.,.. P•h• •'fW't••tr• F• ' "')lo""\....,..... ',...,.....11••,,..,...,, ••, • .,.. ,..,.,..,. fl'IJIP ••Fi'" " "filH•• ?••tr' l"'?Oif " 'rf'*fJo•ll' ............ ,.,... ,..,•.,MT.,.. '''" 'l"" .... '" rr• F,.' F•t••twlll'f"'19r 0
6
8
-4
-2
4
6
-6
-4
?
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- 12
-6
0
2
- 16
-8
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0
-?II
G
10
-2
L
9
10
Figure 18
11
12
13
14
15
16
A = l o w d -ota r ate B = high d:cst:cs r:cstc C = 0-9v feed 0 = ground
co de 54 high d:cst:cs r:cstc in memory
1 SSep2005 1 3 :04
17
1"
19 ms
-6
32
(Return)
Nissan Optical Distributor Oil Lea JPJ'V ~
II
,..--,
'
I
8
'
6
"l
'~
~,
.
I
~
Ir
~
I
2
I L.
•
L:
1
I.-
,_
Oil blocking the drive plate will cause
misfiring and no start conditions
0
0
Figure 19
10
6
8
I
6
I
33
No Start, No Seark
0
G
Section 22
No Start, No spark
(Tested at the coil)
• Possibilities
- Cam /Crank sensors
• Some systems need both cam and crank signals for spark control.
• Some systems only need the crank signal for spark control.
0
G
- This is dependent on whether or not the crank reluctor has a
synchronizer or reference notch in it.
» No sync = module needs both ca m and crank signals for spark
control
» Sync = module only needs crank signal for spark control
Broken or jumped timing belUchain
Module/ Igniter
Coil
PCM
Shorted PCM 5 volt reference circuit
Aftermarket alarm systems, Nissan factory antitheft system
problems
Wiring (opens/shorts, power and ground) problems
2
Direction
•
0
G
•
•
•
•
•
•
Check for spark
From a plug wire
From the coil wire
•
For distributor engines make sure you check for spark at both
locations. No spark at a plug wire could be a cap and rotor
problem.
Check for DTCs (diagnostic trouble codes)
Check RPM and CMP/CKP PIDs
Watch tachometer
Check for coil primary control
Using a test light
Using a DSO (scope)
Perform input bypass tests
With a test light
With scan tool bi-direction control
Check for injector pulse
No spark, good injector pulse = good inputs (cam-crank)
No spark, no injector pulse = input problem (cam-crank)
3
Scan Tool Tests
-
Check for DTCs
Check for an RPM reading in data-stream during cranking . Remember
the scan data sampling speed can be slow so a longer period of cranking
may be necessary to see an RPM signal. To speed up this process limit
the data PIDs on the scan tool using a custom data list. (Figure 1)
- Look at CRANK/CAM PIDs if available
• Example: Chrysler systems, both Cam and Crank PIDs should say
yes the entire time the engine is cranking or running (Figure 1l
- If either one says no there is a sensor problem or a jumped
timing belt (Figure 3)
0
G
-
- DO NOT rely on this data PIO for accuracy on which sensor is
faulty. A bad crank sensor can set a cam sensor code and vise
versa . (Figure 2)
Command the coils to fire
• No spark cranking but sparks when commanded = input problem
(CKP/CMP)
• No spark cranking and no spark when commanded =coil , wiring or
PCM problem
4
Chrysler Cam/Crank PIDs
Figure 1
(Return)
0
G
'
•
1997 DODGE CAR JA
•
2.4L L4 MPI
•
•
A/T
•
UPSTRM 02S(V)_0.47 UPSTRM EXH
CHRY ENG
•
DWNSTRM 02S(V)_0.47 VEH SPEED(MPH)
NO CODES PRESENT
•
ST ADAP( 0/o)
•
SPARK ADV( BT C)_9 LIMP-IN
NONE
BLOCK
A/C
224 TPS(V)_3.77 INJ(ms)_O.O
CENTER
0.0 LT ADAP(%)
0
0
0.0
•
23 RPM _
•
IGN CYCLES 1_ _ 255 IGN CYCLES 2_ _0
•
KNOCK SNSR(V} __ 0.8 EGR SOLENOID
•
IGN CYCLES 3, _ _ 0 OPEN/CLSD LOOP_OPEN
•
RETARD CYL #1
•
CRANK SENSOR _ _ YES CAM SENSOR._ _ YES •
RETARD CYL #3 ___0 RETARD CYL #4 _ _0
•
CURRENT SYNC
PRGE DUTY CYC(%)_0 PWR STEER SW
•
MAP SNSR(V)
•
BARO PRES("Hg)_ 29.0 MIN TPS(V)
•
TPS(V)
•
COOLANT(V)
•
IAT(V)
OK DIS SGNL_ CAM&CRANK •
0 RETARD CYL #2
OPEN
0.0
•
TARGET IAC
0.78
•
ENGINE RPM _ _ 224 DES IDLE RPM - -792
4.5 MAN VAC("Hg)
50 IAC (STEPS)
0
50
3.77 THROTTLE( 01o)
84
•
AUTO SHUTDOWN
ON FUEL PUMP RL Y
1.5 COOLANT(°F)
11 3
•
FUEL ALLOWED
YES FUEL LEVEL(V)_ 1.95
•
MALFUNCTION LMP_OFF CALC LOAD VALUE_
2.19 IAT(°F)
90
ON
4
Known Good System During Cranking
5
(Return)
Inaccurate Scan Data Engin~.lininf ~
Figure 2
•
1994 DODGE
•
3 .3L CHRY ENG
•
NO CODES PRESENT
•
23 RPM _
•
IGN CYCLES 1
704 TPS(V)_.62 INJ(mS)_2.4
•
0
IGN CYCLES 3_ _ _ 0 OPEN /CLSD LOOP CLOSED
•
CRANK SENSOR
YES CAM SENSOR
•
CURRENT SYNC
OK DIS SGNL
NO
CAM&CRANK
The crank sensor signal is faulty yet the
cam sensor data PIO is showing a problem.
4
0
G
Scan Data
255 IGN CYCLES 2
2
10
..,.,.,.v·o
8
·2
6
-4
-
....
·8
0
·2
~JU~
Chrysler 3.3 CKP I CMP.
The CKP sen sor is " glit ching"
causing misfiring.
4
CMP
10
2
Scope
6
·2
CKP- --
2
I '
0
·1 0
-4
Chrysler 3.3 CKP I CMP known
good relationship and signature
wa_veforms
~-·8
- 10
6
0
Jum~ed Timing sm"
8
Figure 3
(Return)
1995 DODGE
2.0L CHRY ENG
NO CODES PRESENT
23 RPM
768 TPS (V )_.5 INJ (mS),_1 .4
25 IGN CYCLES 2, _ _ 0
IGN CYCLES 1
0 OPEN/CLSD LOOP CLOSED
IGN CYCLES 3
CRANK SENSOR
YES/NO CAM
SENSOR
YES/NO
CURRENT SYNC
OK DIS SGNL CAM&CRANK
0
0
,_
I
I
I
I
I
10
0
6
T
;_.
1111:
-
T
.......
I
I
I
Scan Data
10
2
I
I
I
I
II
I
I
I
I
I
I
r+
.....
'
...
0
0
-2
Scope s
lU
T
I
I
I
8
....
6
4
2
~
...
~~
0
2
·6
2
2
0
..._.-8
0
-4
·Z
....
l
I
C ams haft o ff o ne t ooth.
1995 2 .0 M it s ubi s hi E c lips e (Neon
Engine)
· 10
·2
. ...
I
I
I
I
K n o wn g ood c am/crank relatlonshlp.
1998 2.0 L SOH C Neo n
II
7
<=>
Control Testi n1: With A Test Ii1. 11 ~ ~
http://www.youtube.com/watch?v=jJmqdhhduVc
•
•
•
0
G
KOEC (key on engine crank) check coil(+) and coil(-) using a test light connected to
ground
You should see a distinct difference between the two
•
Do not mista ke starter current draw (causing system voltage drops) as coil (-) pulsing
Coil(-) Pulses (test light fl ickers) -means there is control
•
Bad Coil
Coil (-) Doesn't Pulse - means there is no control or the p rimary winding is shorted
http://www.youtube.com/watch?v=YBE7c71fmnY
Constant light, no pulse on coil(-)
•
A completely shorted coil primary winding. (see No Spark Case Study II)
Measure coil primary current with a scope and a low amp probe to identify this
condition
•
Open in the control wire, an open driver (transistor), or an input p roblem
Move the test light to the module/PCM on the same wire
»
No light= open wire
»
Constant light= driver (transistor) problem
You must check powers, grounds and inputs before replacing the
module or PCM .
No light, no pulse on coil(-)
•
No power to the coil
Check coil positive (cranking or running for some systems)
•
Open coil primary, short to ground on the control wire or shorted driver
Connect test light to BAT (+) and touch on control wire (coil unplugged)
»
No light= open primary winding
»
Light = shorted wire or driver
8
m'7~
~
Control Testing With A Scope (Basic Testing)
Coil Negative Voltage During Cranking
Two Different Cars, Both Have No Spark
Which direction do you go next?
I
I
I
I
14
I
I
I
-
I
I
I
I
•
-.-
·-
•
14
....•
.
•
..•
0
-
...•
..•
G
0
•
•
Ss
11 .96l.J
11 .99lJDC
This pie shows coil negative control.
Replacing the coil will fix this no spark problem
:!s
•
•
•
.•
..••
...
.
•
10.44lJ
•
-
0
• •
10.74L.JDC
This pie shows no coil negative control.
Further testing is needed to determine the cause
Note: On coil over plug systems coil negative voltage can only be viewed on a 2-wire coil. On
three and four wire coils, the transistor is located inside of the coil itself, so coil negative voltage
cannot be viewed. This means that test light control circuit testing CANNOT be done on these
coils. Only a scope and a low amp probe will provide control information.
g
Scope Testing Ignition CoiW~ ~
~
• Coil primary voltage testing
• Connect scope(+) to coil , and scope(-) to BAT(-)
- Coil(+) should equal BAT(+)
- Coil(-) should look similar to a secondary waveform with
high voltage spikes between 200 and 400 volts
• Coil primary current ramp
0
G
- Current testing can be done on the positive side or the negative
side of the coil.
- Preferred testing is done at the fuse box for C.O.P. systems.
• If current ramps are upside down, reverse your amp clamp
(polarity sensitive)
• Look for all ramps to be nearly the same
• Look for missing ramps
• Look at turn on and turn off oscillations
• Look for too high or too low of amperage
http://www.youtube.com/watch ?v=y4r50cH NS Lg
10
Coil Prima
'x201
Current vs. Volt
Known Good
v
Current limiting section
/
Collapse of the
primary winding
1.0
350
JOO
250
0
G
Tum-on oscillations
show secondary
winding condition. No
oscillations may
indicate a shorted
secondary winding
Should be a ramp here, a
straight up line indicates a
shorted primary winding
0.8
0.6
Coil
Primary
Current
200
r---..---_....,..__o.o
150·- - - - - -- - - -JVV
Secondary feedback__
100
Transistor on with a full ground
50
Coil off should equal
battery voltage
Transistor on with a
limited ground
(current limiting)
I
Coil(-)
Voltage
-!t
0
·50
·8
-0.6
-7
-5
This is what eliminates the need for a ballast
resistor. The module is limiting current flow, after the
coil has saturated, to prevent overheating
1
-0.8
2 m:
11
.
l'i7
(6\i
r=1
I
vrA..J
I
Coil Primary Current vs. Secondary Voltage
··~· · ············•·····························•····························· · ·····························•·
-------·-·············•-----------··· • ···-···-······ •··············•······-···-··· .............. .
''
I
'
I
I
I
· ·r· ·· ·· ··· ···· ··r· ··· ···· ·· ·· ··1 · ••••• •• •••• ··1 •• •• ••• · ••• •• ·1 ••• · ••• •• •• ···1··· •• •• ••• · ••• 1· • · ••• · ••• •• •• 1·
I
I
I
I
I
·······r·············· ,··············,··············r·············· 1··············
Look at tile turn off oscillatioris.
·--·--- i ·····--·······i···--··--··--·
I
'
'
'
'
'
'··············'··············'···········
-·-·---~---·········
0
..~ .. .... . .. ... ..... . . ..... ... .... ... ... .. . . ... ! . ... ... . ... ..... . . ..... ... ... . ... ..... . . ..... ... ... .. . . .... !.
'
. . . • . . . • . . . • . • ! .............. ! ............. .
I
.... ... .......
....... ,.... .... .... . ,.. .... .... .... ,.............. ,. ........ .... . ,... -· ········
I
I
I
I
I
'
'
• • ~ •••••• • ••• • •• • ~ •• • • • • •••••• • 1 •• • •• • ••• • ••• • 1 ••••• • ••• • •• • • 1 • • ••• • •••••• • • 11 • • •••••• • ••• • • • • • • • ••• • ••••• 1.
'
'
'
• ·r • • • • · • • • · • • • •r • • • • · • • • • • • • • • 1 • • • • • • • • • • • • • • 1 • • • • • • • • • • • • • • 1 • • • • • • • • • • • • • • 1 • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1 •
G
'
'
'
: "'(
--··--- ~ ---···········! .............. ! .............. ! .............. ! ........ .
'
'
'
This large voltage spike and huge turn
off oscillation is the result of the coils,
built up , seconda ry voltage with no
where to go (no release) from the open
plug wire.
' ~~ --· ...... .
~r
............................................................................................................
'
'
'
'
'
This
is what a normal' coil ptima ry
'
'
current
ramp "tu rn off"
should look like .
lt' you.had.a.m.isfire..ttl' is. .te.s. t .w.o.ul.d,.te.11....... .............. :'.
'
Y'.OU
that it is not from:' an open in the
'
~econdary.
···-··············· ················-··············-···························•·
.
.
Open Plug Wire
Known Good
12
m'7~
Shorted Secondary vs. Shorted Primary
This coil has a shorted secondary winding as
noted by the lack of "turn on "oscillations". The
turn-on oscillations in the primary current ramp
are caused by feedback from a good
secondary w ind ing. These oscillations will be
A: un ique to the application and are not always
11
visible.
,
.
.
'
.
1 6 :- - --- - - - - --- - - -:---- - - - ---- - - --:-- - - --- - - - ---- ;- - ---- - - ----- - ;----- - -
.''
...
1 4~
...
...
...
.
.
.
..
.
.
.
..
- - - - - .. - - - - - - - . - - - - - - - - . - - - - - . - - - - - - . - - . - - : - - - - - . - - - - - - . - - - - - - - '
'
'
~
~
'
~
~
This is a completely shorted primary winding as
noted by the straight up line in current flow, and
no ramp on the turn on. A coil should "ramp" up
from counter voltage, which is caused by a
bu ilding/expanding magnetic field. A shorted coil
primary w inding builds no magnetic field so there
is no counter voltage building to appose the
incoming current flow.
...
.
.
'
.
.
.
.
.
1.0.··············: ..............: ............................;.............. ;.............. :.............. :............................. ,.............. ;
...
...
..
..
...
....
.
.
.'
.'
.'
.'
.'
.
.
.
0.8···
············!··············I··········
...
......
········!··············!
..............
;
..
············I········
····················!··············l
.
.
.
...
...
...
...
...
..... ..... .....
..
.
.
.
.
.
..
..
.. .....................................;
··················!··············!··············!··············!········
..
...
.....
.....
..... ..... ....
.....
..
'
'
'
.
'
'
1 2} - - - - - - - - - - - - - - } - - - - - - - - - - - - - - } - - - - - - - - - - - - - - t - - - - - - - - - - - - - - t - - - - - - -
0
G
•
•
1 0~--------------~--------------~-----
•
--------f------------f------.
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...
.
..
.
....
...
.
.
.
.
.
8~ - - ---- .. --- ~ - ---- - -~---- ------ ·- : --- -----. --- : .. ---..
....
...
...
...
.
.
.
.
.
.
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.
.
,
.
6 :---- -- ----- ---.. -- ------- -- --:--- ----------- ;- ----- --- --- -;----- -..
..
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..
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.
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.
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4~ ---- -- -----~---··sncirte'a- s-econ_a_a_ry
________
----~------.
.
.
..
2~
..- W i ndi~g
..
...
..
..
.
.. --------------.. --------------}-.. ------------- ..t - - - - - - - - - - - - - - t.. - - - - - - ...
..
..
.
..
'
'
'
'
'
'
'
'
'
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o~
'
'
~
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'
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'
''
-2
-1
1
2
0
'
~
O.l~·· · ······· ··· ··i··· · ······· ···i ···· · ·····
1
•
•
O.it·..
.. ....: .. ··
....:.....
:
:
:
..:.......
•
..:........
•
•
•
·:.......... ·: .......... : •···· .... ·
...........
•
.. ...... :
: Shafted prim$ry
:·windfng
'
'
.: . . :·
. ..
.
. . .
:
..
..
. ).O
.
.
....... . . . . . . . . . . . . . . . . '---4..- --..--;16
o.~-·-,_....--·­
...
..
.
.•·······•······..·•·······••····..•··•·······•···..•···•·······•········ ········•·······•········1...2
·O.~ ·•·······•····•.···•·······•·...····•·······•········•·······.
...•
..
..•
•
.
.
.
...
...
.
·0.(
..
.. ...
~
..•
...
...
.
.
.
•4
·O.
·64
·61
·60
·56
·54
·51
·50
·46
·44 ms
....... . ..
- -· .
O~
.
. ·:
.
. :·
-
'
~8
In both of these pictures we are looking at coil primary current
flow
~8
13
Multiple Coil Systems
.
.
.
. ---- -- ---. ;. ------- -- -- -- .; ...1.0
..
.
...
.
' • • • • • • • • • • • • - • ,.
' - - • - - - • - • • • • • • 'r • • • • • • • • • • • • • • ·,-' • • • • • • • • - • - - - - -. - - - • - • • • • • • • • • 1 • • • • • • • • • • • • • • ·r · • · • - • - - - - • - - - ~- -.·
'
.....
-- -- ---- -- __ ,,' ________
'
'·
I-
'
··-·~--·
-... -.. -- .. -- . -,-' ------ . --------.-' ---
'
~---------------~-------
'
'
'
·,·'
'
'
~---------------~----
.
0
.
..
-...... -- .. -- . ------ . --------.--
.
-...... -- ... -- -.'- -- . ------------.-
----. --- . -- . --- . --- .....
---- ________ .. ___ -- -------. -- ..... --- ---'
out
.
..............' -- ---- ________ .. ____ _ -· -· -· -· •.......... -- -- ' -- -- __________ _._ _.. - __________ ; _______________
'
•
•
-~--
-------------
. .8
~ --·0
----------'---------------'
.
. --·0.6
-- --- .. -- . ~ ... --- . --- ---- -: ···0.4
.
. .2
---------------}-------------- .-• -. - ----------'---------------'--·0
'
'
•
-~ -..... :.............. -~. ---.--------..!. .. -.-......... ~ ........... -.-.:. -.n n
GM 3800 Waste spark V-6 with a two cylinder misfire. T he top picture shows good control on all three coils. The
bottom picture reveals the problem. This system needs one co il, the module is fine. The plugs and wires should also
be replaced because high resistance in the secondary can cause the coil to fail in this way.
'
,,...., ......•............
'
.. . . . . . . : .............. -~ .............................. ;· :;·:.::.=;1;;;-·::..:
Il"f'
www=""-·x::Ol""'..ct::>!u,,.,,b'-"e"".c,,,,,o'+'IDJ...!!..!..I.""""~?L...>:ill.!.LJ.!.~.....!.L!,,,,
•
•
•
.
. .. \. ........ .
. . . - - . . . i . . - - . - - . . - . . . - -'-. - - . . - . . - - . . - . · '- - . . - - . .
'
Zoomed in
'
···············r········-···
'
'
'
·,· . . . . . . . . . . . . . . i . . . . . . . . . . .
•
•
···-····1·············-·r·
•
••• L •••••••••
'•
······'············
•••• J ••••••••••••••• 1 ••••••••••••••• 1. •••••••••••
····1········-······;·····-·········r
'
'
'·
...........-.-• ...... .
'
Look at the turn on oscillations .
'
•••... , .....•......
·············r············-·~-·······
•
...... , ........... .
___ .,_____ · .,._
,__-<---·:·Krl'owrl'-Gooa····
'
--····•············
'
····•·r·••···········~······••
• • • - - ••• - . ,. - - • - - •••••• - - • , - •••••• - - • • • • ·r •• - - •••••
'
........• , ~~--<·· - ................................................................
Shorted Coil Secondar}' Winding
...
.... .
14
V6 Waste Spark With Missing RlRiJf
n~r10.')I
L&::f X I ~u m-:./dl-v
...
>C,
..- 1 A
a
_.
~UA
O ff
-
DC -
Off
_.
0
O C
_.
Ott
._
Off
A
...
1.
.
......
....
..
..
1.
.......
...
.
;
;
....
....
..
.
...
.....
..
.
.....
...
..
...
.
1.
.
_......
...
.
..
..
:
:
>
~z- ~.. --------------- ~. --------------- ..~ ---------------:..--------------- ~.. ---------------:---------------~--------------~---------------~--------------..
..~ ------------.
.
...
IO
...
1.
...
....
...
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..
1.
..
..
..
...
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1.
..
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...
:
...
1.
...
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...
.
.
u-1----- ------- ·1------------- ·r·---- ---------i----- ------- 1-------------- r------ --------r ------ ------- --------------- ------- -------r------:
·- ~ ----
;
:
. ------- - ~ ------------
- .~ -----
...
....
..
.
;
---------i----..
..
....
..
.
-------- ~. -------------·-!------
;
--------r-----··
------- --------------· ------- 1- ------ ..~ ------- ·---...
..
....
...
.....
...
.
,,_
· · - :r______________·J:···f
·-:t_______________
------ :[ ______________ J:_------· ----··ri
_J,_______________ Jr---_______________ :r_______________
______________
______________ J:_______________
..
..
:
:
.....
..
..
...
..
...
..
...
..
...
..
Missing R$mp, Good Transi$tor Driver, Open Coil Primary
-·......
:
_.,. ......
-J--------------- J --------------- ~ ---------------·---------------J---------------~---------------~---------------·---------------J---------------~------------m~
......
0
G
...
..
·
-·
•
ft ft
What you are seeing indicated by the arrows is transistor base circuit current flow. In the
top picture there is a few hundred milliamps of activity during the time the coil should be
v
firing. This is ind icating that the transistor is functional. In the bottom pictu re there is no ·-----·
--------activity during the time the coil should be firing indicating the transistor is not functional.
2 .0 :
.
..
..
:
.:
.:
:
.:
.:
t . G~ - • - - - - - - - • - - - - -~- - • - - - - - - - • - - - - ~ - - • - - - - - - - • - - -
'
:
~
.:
o .a:
~
....
..
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15
S)lnchronizing Waste S~ark coWs E3
Fig. 2: 3.BL [VIN L & V IN 1 ) PCM Wiring D iagram (2 DI 3)
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Connect Amp
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Here
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A MPUFIER
TACH
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Synchronizing Waste Spark Coils
v
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1.4
1
6
5
4
3
1
2
1.2
1.0
0.8
,
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Shorted Prima ry W inding
0.6
0
G
A
0.4
0.2
20
0.0
16
-0.2
12
.___ #4 TDC
h
ex aust
-o. 4
#4 TDC
compression
.
Open Plug or Wire
~
-ft ~-~~--~~~--~~L4
-100
-80
-60
-40
GM 3800
-20
0
20
A = Coil curren1 B = 1 4 cyl sync
Firing order = 1.6.5.4.3.2
40
60
This engine had a three c ylinder misfire. Can you pic k out the causes?
80
ms
17
2007 Honda C.O.P (coil over p1f!l91
PCM
Measure Coil Primary
Current In One Of
These Two Places
.------------------------------------------·
'
Co11 Over Plug Primary lgn1t1on
Circuit
G
''
'
A bypass test can be done with
a test light connected to
battery positive. Touching on
and off of this wire will force
the c ii to fire
Fuse
0
13
------------------------------------ -------· ·------------
r-------------------•
: c S I GHii-' :
L-~~~~--'1'-~--<-~-"!"'-~,
'', ___________________ J
'
Coil negative voltage cannot be viewed due to
location inside the coil. This means that using a
test light to check for coil negative control is not
possible. A scope and a low amp probe is
needed .
_________ , ' ·---------' ' -------------------
Measure PCM to coil signal
here. This should be a 0 to
4 volt square wave during
cranking or runn ing
CKP
CMP
18
2007 Honda C.O.P. Wavefoffk
v
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1 .~ --------------~--------------~--------------;--------------;--------------;--------------;--------------;--------------~--------------~-------------- ~ 6
1.m---········· This PCM supplied 4 volt square
... ,' ......... -- ... '' -------<ii'-~~-;~~- 10 amp peak
•••••••• , 2
wave is used to turn on the base
'
•
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............. ·8
O.Si' · · · · · · · · · · · · circuit of the tra nsistor inside of the ·---;-----------coil assembly.
.
.
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0.6: - ---- --- ---- - -r--------------r--------------t ---- ---- --- -,...,________,____..,.___.,,._...,., _- ---- ---t --- ---- ---- --- i --- ---- ---- --- i · - - - - - - - - - - - - - ·:4
•
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.t:- ----------------'
o.
·! -- --------- --
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· 1oomv--- --1·-am p.......................................................................................................................
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-0 . 4·--------------~--------------~--------------·--------------·--------------·--------------·--------------·--------------~--------------~-------------- ·16
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-5
-4
-3
-2
-1
0
1
2
3
4
5 ms
A = Coil Primary Current At Idle (Known Good) B = ECM Control
Signal To Coil (3 wire coil...1 =power feed 2 =ground 3 =ECM
Control) Coil negative voltage cannot be viewed.
19
No Spark Case Study I
70
O.Br -----:- ----:----- -----.-- --- -----,''
'
'
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70
'
60 0.6~----~-----~----~----~----···--·~-----~---- -----~---- ~4
60
lpv/; arnpi:;
~ Th is coil current ramp is
•
'
'
·r. peaking at 1 amp.
50 0, 4,r···-,·····r···
Th is is not a problem
...• with the coil. It is the
40 0 21. .. ..
module that is providing
a poor ground as noted
30 0.0,'- _ _,........._,__....
'
by the high voltage
du ring the dwell period.
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o LU
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Normal
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.....·•·............. .'
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Replacing the module fixed this no spark problem
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Good ground and
proper current
limiting with this
new module.
20
No Spark Case Study II
(Return)
x
4001- - - - - - - - - - - - - - - - - - -10.8
350·. ~- .... -~ ..
•
•
Known Good Cylinder
.. ··1.2
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150·. , ..... -:· ..... ------·-----•
100· • ~ · -"•" ·~ • -• •" i • • · " • ..: .. " " • " • r • ·" •" i • • • • • ..:.. • • · " · ' • • • • " ~ .. • " • • ·~ • • "
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control right?
.
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--.,.
l
300--~- ---- - ~ ----- ~ -- ----:------~ --- -- ~ -- ----:- ----•! --- -- ~- - -- - -~ - - --2.0
50 '
0 . .,. . ....... . -- -., ----- ------ ... ---
•
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Misfiring Cylinder
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Coil Negative Voltage
-1 00--~- -----~ -----~ -----_:_ -----~ -----~ -----_:_ -----: -----.. ------'- ---
-~-~,'-~---~-~---'·~-~-~---~--.~-"'- ----·- -----~ -----.. ------·- -----"-----
Chrysler C.O.P. System With 1 Cylinder Misfire
.,# .. - - -
- _._ -
- -
21
[QJ'V~~
~
No Spark Case Study II
Known Good Cylinder
Misfiring Cylinder
x
400,. • .,. "" •" . ,. "• • "•., ••" •• "t'""" •" • r" • • "•., • •" • • "t'"" • •" • '" • • • • ., .. •" • • .. ,.. "• •2,0
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----:-----~------~---1
.2
250-. ~- .... -~. . ··"· --- .. --- ............. .. .... ..............
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0.8
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.___ ....:. ---- .... --.... .-.. ----:-.----- ----- . ----- ---1.2
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Coil Primary Current
..
..
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. ---.. "· -----·---.........-----"-----300--.. _----_.....
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r-'''-----'''---------
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J' •••••• '\. •• 0 4
200· .J' • • • • • • -.. ............
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.. -..... -- 0.8
250 ................ --·"··--- .......... .... -"------·- --- -·-- ---!-'--'
300- -~- ---- -~-----;
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' • •• J ••••• • • - • • • 'I. ••• - J•••••• -··• . . . . . l' • • • • • IJ............
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-0.4
50· "' ........ ,.. .. .. . .. ., ...... .. ..............
.. ., . . . . . . '"t"'
..... , ...... .. ------.. -- -0.8
. , .......,..
., ......... ,.. .. . -1.2
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-50--....' ----.... -----..' ------·------..
-----... -----~ ----1.6
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"-1----~----~---!.'-''---I
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100--~- ---. -~ .. ---- ~ ---.. -:- ---. - .. ---- ~ --.. --.:. ---. -~ .. ---- ~- ---. -~ ----0. 4
•
How can we have a cu rrent waveform
50- -~ and no voltage waveform (no
-0.8
•
control)?
I .... ' i •• , . 'i tl
t .• ,,. f i' . 1• • •1ti:,p•
1• t n•ntsil ' : I pfii1p• I J;• f
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-50-- ---- ----. :--- .
.
~-
-~
Coil Negative Voltage
. . . . . . . . . . . . . . . . . . . . . . .1 . . . . . . . . . . . . . . . . . . . . . . . .1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~ . . . ..
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.6
'
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-..... ,, .. -.. -·- .............. ,, .. -.. -·- ...... -.......... -......... -22
No Spark Case Study II
Known Good Cylinder
Misfiring Cylinder
x
., 0
4rn
400--.,. ----.,. -----"' ------,-----·r - - -2.0
There is defin itely control, but what's
Zoomed In wrong? Shorted primary winding And why
350--.... ----... -----~ ------·------.. -----~ ------·- ----- -----.... ---.
6
does the voltage waveform look like this?
The transistor is adding resistance to the
300• • -'• • •••
"-----_,_ -----.. -----... ----... ---1 2
2
3! ground circuit to limit current flow.
r - - - - - ., - - - - - -,- - - - - • • - - - - - .,. - - - -
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23
No Spark Case Study II
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A shorted primary winding in this coil is causing the PCM to immediately enter
o------·-·
cu rrent limiting mode to protect the driver from excessive cu rrent flow. What do
•
:• you think a test light connected to this coil control wire would look like? It would
_ ______ ~ __ be a steady light indicating no control. Would it flicker? No
5
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A = coil primary voltage B = Coil primary current (shorted coi l)
24
No Spark Case Study Ill
2 50
2UU
Re s lstatlce :
Secor1dary
150
Resistance spec:
Prim ary 2-3 ohms
Secondary 6000-8000 ohms
2.3 o l,ms
7 .600 Ol'lm$
Pr·i mary
No Spar k
1 00
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Shorted secondary
winding
- 3b
n.n
A bad coil that measures good resistance! This is because an ohmmeter does not "stress" the
windings. Ohmmeters are extremely inaccurate on high voltage or high current circuits. Leave the
ohmmeter in your tool box for coil tests. You need a scope and an amp probe for proper identification.
Resistance:
Primary
Secondary
G o od Spark
2.4 ohms
6 ,900 ohms
100
50
1.0
0
0 .8
- 50
0 .$
-100
Good spark line o....
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Good secondary winding
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25
DIS or COP No Scope Tests
Misfire, no spark from one coil
• Swap known good coil to the location of the no spark
coil
- No spark moves with the coil = bad coil
0
G
- No spark stays in the same location = wiring
problem or bad driver (anytime a coil driver fails you
must check coil primary resistance and current on
the coil before replacing the driver)
• Check coil primary and secondary resistance with an
ohmmeter (this test is usually inaccurate)
26
0
G
No Start, Good SfJark and
Injector Pulse
Section 23
•
•
•
0
G
•
•
•
Check compression
- Conventional method
- Relative compression using a DSO and a high amp probe
Check for head gasket failure with an exhaust analyzer
- Look for HC emissions in the coolant overflow bottle
Check for a jumped timing belt or chain
- Scope cam and crank
- Perform visual inspection
Check for restricted exhaust
Check fuel pressure (no psi from the pump)
Check for engine flooding conditions
- Look for the following:
•
•
•
•
•
Fuel pressure too high (stuck shut regulator)
Ruptured fuel psi reg. diaphragm
Leaking TBI injector
ECT sensor problems (reading -40 degrees during start up)
MAP sensor problems (reading WOT voltage continuously}
2
EGR System Problems
0
G
Section 24
Test Name: EGR Flow
Test Point: Map Sensor
Test Cond.: hot engine
2000 rpm
Symptom : mil, OTC P0400
Make:
Chevy
Model:
tracker
Year:
1998
Engine:
1.6
General ID: slightly
dirty/clean
Date:
1/10/2006
5
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20s
2.541J
2.8 1lJDC
Slightly plugged up intake
passage. Enough to set a
OTC
0
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20s
2.961J
0
3 .1 6lJDC
After cleaning EGR tube,
valve and intake
passage (Figure 1)
• Both pictures were taken with the throttle held open with a screwdriver at 2000 rpm
•
•
•
•
before opening EGR. The "ramp" is when the EGR is forced open. These pictures
show the manifold pressure changes with the EGR fully open.
MAP voltage at idle was 1.56-1.59 voe (EGR Closed)
MAP voltage at 2000 RPM was 1.42-1 .44 v oe (EGR Closed)
There are two solenoids on this system. The front solenoid is normally open, and is
de-energized by the PCM to allow ported type vacuum to the EGR back-psi
transducer. The rear solenoid is normally closed and is energized by the PCM to
allow intake type vacuum directly to the EGR.
All testing for flow was done with the rear solenoid energ ized while monitoring MAP
voltage.
2
Introduction
The primary purpose of this section is to understand EGR system controls and operation, and how
to troubleshoot the entire EGR system quickly and accurately.
The most common cause of EGR flow trouble codes is a plugged up intake passage. It is never
the exhaust side of the EGR that accumulates carbon deposits. The deposits form when the hot
exhaust gases rapidly cool when entering the low pressure intake manifold.
Another common failure is carbon deposits causing the EGR valve to stick .
0
G
•
If it sticks open the engine will idle very rough and possibly have repeated stalling problems ,
however it will run good at part throttle and under load.
•
If it sticks closed you will usually not have any driveability complaints other than a check
engine light on. Although some engine "pinging" may be noticed at part th rottle.
Another common problem is carbon deposits around the seat area of the pintle. The valve will
operate normally. There will be good flow. However the carbon on the seat area will cause a
higher than normal closed valve position and the PCM w ill set a code for this.
As for testing these EGR systems, there is some common procedu res used. For EGR solenoid
function and control as well as PCM driver operation see Section 3 "Output Solenoids and
Transistor Drivers". Force the EGR valve to open at idle. The engine should stall or almost stall
on every system . This will ind icate that there is good EGR flow. If the engine does not get rough
then there is a problem within the system . As for pinpointing the exact cause of the system you
should not need an engineer written flow chart because by this time in my book you should
already know how to test all of the solenoids and sensors involved with every EGR system . These
include: Potentiometers (EVP sensor}, The rm istors (EGT sensor) and Pressure Sensors (MAP
and DPFE sensors)
Within the rest of this section are case studies of EGR problems that you are going to see and
links to some of my videos where I am demonstrating some EGR system tests .
3
(Return) Figure 1
Plugged EGR Port
Before
After
0
G
Chevy Tracker 1.6 Intake manifold passage
4
Linear EGR EVP Signals
MIL only, no drive ability complaints
•
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•
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•
1.27UDC
KOEO closed EGR, EVP
voltage. Before repairs
5s
0.88U
0.91UDC
KOEO closed EGR, EVP voltage
after cleaning pintle and seat.
http ://www.youtu be.com/watch ?v=QYtYSgg IJ o Y
Start watching at the 8:06 mark. The data capture on this page is from a GM EGR
valve with carbon deposits on the pintle seat area of the valve. Watch the video to see
how to clean it.
5
Scan Data Of A Stuck Open Linear EGRlCG1aFve
~
All of the data PIDs pointed out in the capture below, are the result of a stuck open EGR valve.
These include lean commands from a rich exhaust, high IAC counts because the engine is having
problems holding an idle and higher than normal EVP voltage and o/o.
0
G
•
1992 GMC
•
VARIABLE TUNING OFF
•
4.3L V6 CHEVY CPI
•
EGR ZEROED
•
•
•• DIAGNOSTIC MODE .
DO NOT DRIVE! ••
•
•
EGR VLV POS(V)_4.38 ~
EGR DUTY(o/o)
0
~ Stuck open
•
32 EGR SYSTEM P
•
DES EGR( 0/o)
0
•
0 RPM_ 913
•
EGR POS(%)
70
•
INTEGRATR 108
•
SPARK ADV('1)
8
•
oPEN tcLsD
•
CCP DUTY CYCLE
•
•
KNOCK
•
EXHAUST OXYGEN_LEAN
commands
BLOCK LEARN
1oa /
•
KNOCK RETARD('1)_
•
FT CELL
•
BATTERY(V)
•
TPS(V)
•
FUE L PUMP(V)_13.5
•
THROTTLE(%>) _ _ _0
•
HIGH BATTERY _ _ NO
•
IAC POSITION
109 ~<- H igh counts
•
CAT CONV HITEMP
•
DESIRED IDLE
875
•
COOLANT(°F)
•
TIME- - - -2:54
•
START CLNT(°F)_86
•
02 CROSSCOUNTS
•
MAT(°F)
•
A/F LEARNED _ _YES
•
A/F RATIO
•
BASE PW(mS)
•
DECELENLEAN
A/C
A/T
Engine at idle
LEM
2(mV)_
482
l.oo~ Lean
8
0.48
0
•
YES
~ pintle
0
NO
0
14.1
NO
130
88 MAT(V)_ _
1.60
MAP("Hg)_ _ _ 21.7 MAP(V) _ _ _3.42
14.7
2.9
NO
http://www.youtube.com/watch?v=QYtYSgglJoY
Watch this v ideo at the 8:50 mark for a sticking pintle . Th is is
what it looks like and how to clean it.
6
m'7 ~
~
Stuck Open Linear EGR Valve
Typical GM 4 .3 Vortec Engine
Carbon problems
Normal Closed Valve
Position
0
G
7
Plugged EGR Intake Tube
•
•
..~ •
0
0
•
Nissan Maxima with EGR
low flow DTCs.
Notice the EGT sensor in
the intake tube .
This sensor is used for
diagnostic purposes and
EGR flow control.
For testing procedures
see Thermistors in
Section 6
8
FORD EGR PROBLEMS
Vent Cap
EVR Solenoid
...it Orifice
Exhaust Manifold
0
G
•
KOER, connect voltmeter to DPFE
signal wire . Should be around .5 to 1v
at idle with no EGR flow.
- Jump EVR control wire to ground
with a test light to energize the
solenoid .
- Engine should stall or almost
stall and DPFE voltage should
increase .
- Increase RPM to 1500 to prevent
stall and re-do test. DPFE
voltage should increase to over 4
volts and the engine should get
very rough .
- If engine gets rough and/or stalls
and DPFE voltage doesn't
change= DPFE problem, not an
EGR flow problem .
http ://www.you tu be.com/watch ?v= pH kj RwD-Xw
http://www.youtube.com/watch?v=znw-gjLEOfk
9
Section 25
Term and Abbreviations
ENGINE COMPUTER
TPS
ECT
TAT
MAT
ACT
H02S
KS
MAF
0
0
MAP
BARO
EVP
PFE
DPFE
VSS
TAC
ABV
ASD relay
EEC rv
OLC
PCM
ICM
CKP
CMP
throttle posi tion sensor
engine coolant temperature sensor
intake air temperature sensor
manifo ld air temperature sensor
air charge temperature sensor
heated oxygen sensor
knock sensor
mass air llo\v sensor
manifold absolute pressure sensor
barometric pressure sensor
EGR valve position sensor
pressure focdback for EG R (Ford)
della pressure feedback for EGR (Ford)
vehicle speed sensor
idle air control
air bypass valve
auto shutdown relay (Chrysler)
electronic engi ne con trol system (version 4. Ford)
data 1ink connector
po\vertrain control module
il?Tlition control module
crankshaft position sensor
can1shaft position sensor
-
I
0
0
OBD JI
on board diagnostics 2 ( 1996 and ne,ver engine computer systems)
HZ
hertz (a measurement of frequency)
ISC
Idle speed control
EGT
Ex haust gas ten1p.
ALDL
Asse1nbly line data link (same as DLC)
BCM
Body control •nodule
ECM
Engine control 1nodule (same as PCM)
TCM
Transmission control module
PIN switch
Park/ Neu tral switch
P.S. Psi
Power steering pressure switch
MLPS
Manual Lever Position Sensor (Ford. tr,msm ission gear position switch)
OTC
Diagnostic Trouble Code
DSO
Digital Storage Oscilloscope
EVR
EGR Valve Regulator (FORD)
0
ormally Open
C
ormally Closed
PCV
Positive Crankcase Ventilation
P\VM
Pulse Width Modu lation
BOO S\vitch Brake On/Off S\vi tch (Ford)
TCC so lenoid Torque Converter Clutch solenoid
TFT sensor Transmission Fluid Temperature sensor
PlD
Parameter identification (scan data values)
EMISSIONS
HC
CO
OX
C0 2
02
hydrocarbon
carbon monoxide
oxides of nitrogen
carbon dioxide
oxygen
2