Carman scan ONE
application
CONTENT
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
CRANK ANGLE SENSOR
CAM POSITION SENSOR
TPS
AIR FLOW SENSOR
OXYGEN SENSOR
INJECTOR
IGNITION
ISC VALVE
AIR TEMPERATURE SENSOR
COOLANT TEMPERATURE SENSOR
BATTERY VOLTAGE
KNOCK SENSOR
VEHICLE SPEED SENSOR
EGR VALVE
CANISTER PURGE VALVE
OXYGEN SENSOR HEATER
CRANK ANGLE SENSOR-1
CHECK METHOD
With connecting the Oscilloscope, Set the
Sampling rate to over 250KHz and Compare
the Counts and width of tooth between Long
tooth after measuring the Crank Angle signal
when Engine trouble is appearing.
NOTICE : Ground line should be earth to
engine or chassis to see the absolute signal.
< Reference > This signal must be measured
on over 250KHz sampling rate at least. In
case of low memory capacity, Measuring
time is very short. Thus It must be measured
on time of appearing the Engine trouble as
triggering the signal. But it is difficult to
catch on time of Engine trouble.
CRANK ANGLE SENSOR-2
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1. Find and connect the Signal and Ground line referencing the wiring diagram.
2. After measuring the Signal, Compare the measured signal with Normal Signal.
3. Check if Operating of Related components with this signal is Normal through
checking the normal condition value of components
< Related components >
1. Injector Timing and working status.
2. Ignition timing and working status
3. Synchronization with CAM angle signal
CRANK ANGLE SENSOR-3
WAVE ANALYSIS
 WAVE ANALYSIS-MAGNETIC TYPE-1

When the target wheel (The ring that has teeth) pass by the magnetic crankshaft
sensor, electric pressure is generated during cutting the lines of magnetic force.
The shorter the distance between crankshaft sensor and the target wheel (air gap)
is and the higher the engine revolution is high electric pressure is generated. The
longer and the slower, low electric pressure is generated.
CRANK ANGLE SENSOR-4
 WAVE ANALYSIS-MAGNETIC TYPE-2
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
ECU can recognize tooth signal not by means of peak signal but by means of
rising edge and falling edge.
That is, if the output voltage of the magnetic sensor is over about 20mV ECU
determines ON, if about –5 ~ -10mV ECU determines OFF, and finally ECU
recognize one ON/OFF cycle as one tooth.
CRANK ANGLE SENSOR-5
 WAVE ANALYSIS-MAGNETIC TYPE-3

If noise is occurred and ECU recognizes this noise signal as real tooth signal, ECU
cannot detect long tooth or detect more increased short tooth and it results in fuel
cut and ignition cut. So when noise is exist, it must be checked abnormal injection.
CRANK ANGLE SENSOR-6
 WAVE ANALYSIS-MAGNETIC TYPE-4


The level change (Edge: from high to low level/ from low to high level) of the
camshaft signal must be occurred at least two short teeth before from the
long tooth.
If the level change of the camshaft signal is occurred at long tooth or at short
tooth before one tooth from the long tooth, We must check pulley (TDC)
position and modify it.
CRANK ANGLE SENSOR-7
 WAVE ANALYSIS-HALL TYPE-1

This one is hall type sensor and circuit is included within sensor and 12V
power is supplied. If metal is passed the sensing part within 1.0±0.5mm gap,
5V (or 12V with another sensor) output voltage is generated through sensor
internal circuit.
CRANK ANGLE SENSOR-8
 WAVE ANALYSIS-HALL TYPE-2


ECU can recognize tooth signal not by means of peak signal but by means of
rising edge and falling edge.
That is, if the output voltage of the magnetic sensor is over about 200mV ~
2.5V ECU determines ON, if about 100mV ~ 1.5V ECU determines OFF,
and finally ECU recognize one ON/OFF cycle as one tooth.
CRANK ANGLE SENSOR-9
< When ignition wave is occurred during crank angle signal ON >
 WAVE ANALYSIS-HALL TYPE-3

If noise is occurred and ECU recognizes this noise signal as real tooth signal,
ECU cannot detect long tooth or detect more increased short tooth and it
results in fuel cut and ignition cut. So when noise is exist, it must be checked
abnormal injection.
CRANK ANGLE SENSOR-10
< When ignition wave is occurred during
crank angle signal OFF >
< When ignition wave is occurred at the
beginning of crank angle signal ON (or OFF) >
WAVE ANALYSIS-HALL TYPE-4
CRANK ANGLE SENSOR-11
 WAVE ANALYSIS-HALL TYPE-5
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
The level change (Edge: from high to low level/ from low to high level) of the
camshaft signal must be occurred at least two short teeth before from the
long tooth.
If the level change of the camshaft signal is occurred at long tooth or at short
tooth before one tooth from the long tooth, We must check pulley (TDC)
position and modify it.
CRANK ANGLE SENSOR-12
 WAVE ANALYSIS-OPTICAL TYPE-1

This is an optical sensor. During round plate (It is called target wheel) that has
holes is revolved with camshaft, the light is shone. If the light passes through
the hole, out put voltage is generated. This sensor uses this principle and need
power to be operated.
CRANK ANGLE SENSOR-13
 WAVE ANALYSIS-OPTICAL TYPE-2


ECU can recognize tooth signal not by means of peak signal but by means of
rising edge and falling edge.
That is, if the output voltage of the magnetic sensor is over about 200mV ~
2.5V ECU determines ON, if about 100mV ~ 1.5V ECU determines OFF,
and finally ECU recognize one ON/OFF cycle as one tooth.
CRANK ANGLE SENSOR-14
 WAVE ANALYSIS-OPTICAL TYPE-3

If noise is occurred and ECU recognizes this noise signal as real tooth signal,
ECU cannot detect long tooth or detect more increased short tooth and it
results in fuel cut and ignition cut. So when noise is exist, it must be checked
abnormal injection.
CRANK ANGLE SENSOR-15
 WAVE ANALYSIS-OPTICAL TYPE-4


The level change (Edge: from high to low level/ from low to high level) of the
camshaft signal must be occurred at least two short teeth before from the
long tooth.
If the level change of the camshaft signal is occurred at long tooth or at short
tooth before one tooth from the long tooth, We must check pulley (TDC)
position and modify it.
CRANK ANGLE SENSOR-16
FIELD EXAMPLE
< Example 1 >
Vehicle : New Sephia 1.5L SOHC, Odometer : 7,200Km
Problem description : Engine is started with hesitating. Engine is stopped soon
after starting in cold ambient condition and restart is hard.
Cause : Power, which is supplied, to distributor is cut during very short time when
key is released after engine start. This phenomenon cause abnormal crank angle
signal and it result in engine problem.
Signal measurement
CRANK ANGLE SENSOR-17
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Explanation : When key is released after engine start, ECU doesn’t
inject fuel due to missing crank angle signal by the bouncing
phenomenon(Repeat contact and non-contact)
Enlargement of application: The change of sudden engine speed is
due to injection fuel cut or abnormal ignition timing control. Most of this
phenomenon is case that ECU doesn’t acquire normal crank angle
signal, so crank angle sensor signal should be checked whether it is
normal or not. And ignition timing and fuel injection control should be
checked at the same time.
A. In case of back-fire occurrence of LPG vehicle
B. In case that engine stall is suddenly occurred in idle sate
C. In case that engine vibration is intermittently occurred
D. In case that engine is started with hesitating as jamming flywheel in
self motor
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CRANK ANGLE SENSOR-18
< Example 2 >
Vehicle : Sephia 2 1.5L SOHC, Odometer : 24,000Km / Credos 2.0L
DOHC LPG
Problem description :
- Gasoline vehicle : Engine is started after hesitating during 0.5[sec]
as jamming flywheel in self-motor or engine is not started with the
phenomenon.
- LPG vehicle : Backfire is happened when engine start.
Cause : Injector opening phase is abnormal and ignition timing is
controlled with intake stroke.
Signal measurement
CRANK ANGLE SENSOR-19
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Explanation : When flywheel is jammed in self-motor with initial engine
cranking, vibration is occurred. ECU regard it as tooth signal and then
first normal crank signal is acquired as long tooth. It results in wrong
TDC calculation in ECU and abnormal fuel injection time and ignition
timing control.
•
Enlargement of application : It is example that is occurred by wrong
acquisition of ECU. Even though signal is normal, in case that ECU
acquires it as abnormal signal, trouble may be detected. Therefore if
injection time and ignition timing control is out of normal range, crank
angle signal should be.
A. In case of back-fire occurrence of LPG vehicle
B. In case that engine stall is suddenly occurred in idle sate
C. In case that engine vibration is intermittently occurred
D. In case that engine is started with hesitating as jamming flywheel in
self motor
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CRANK ANGLE SENSOR-20
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< Example 3 >
Vehicle : Avella / Sephia 1.5L SOHC/DOHC , Odometer : 24,000Km / Credos
1.8L/2.0L DOHC LPG Taxi (Optical distributor equipped)
Problem description : Engine stall is occurred at times and once the problem
is happened it is repeated many times. And after maintaining normal state for
long time, engine stall is suddenly occurred. And then engine is not started.
Cause : Crank angle signal is occasionally missed or noise is occurred.
Signal measurement
CRANK ANGLE SENSOR-21
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Explanation : In case of missing crank angle signal and noise
occurrence, ECU recognize wrong tooth number. At this time injection
and ignition is cut until tooth number is identified. If tooth number is
corrected during injection and ignition cut, it is started again but engine
stall may be occurred before ECU recognize it.
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Enlargement of application : In case of sudden engine stall without
abnormal engine operation, it is due to mainly abnormal crank angle
signal. In this case, crank angle signal, injection time and ignition timing
should be checked together and if missing injection or ignition is found
out, check noise occurrence after amplifying crank angle signal.
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A. In case of back-fire of LPG vehicle
B. In case that engine stall is suddenly occurred in idle sate
C. In case that engine vibration is intermittently occurred
D. In case that engine is started with hesitating as jamming flywheel in
self motor
CAM POSITION SENSOR-1
NOTICE : To measure the signal, ground line should
be earth to chassis or engine.
CHECK METHOD
•
With connecting the Oscilloscope,
Set the Sampling rate to over
250KHz and Compare the Counts
and width of tooth between Long
tooth after measuring the Cam
Angle signal when Engine trouble
is appearing.
•
< Reference > This signal must
be measured on over 250KHz
sampling rate at least to see the
effect for noise. In case of low
memory capacity, Measuring time
is very short. Thus It must be
measured on time of appearing
the Engine trouble as triggering
the signal. But it is difficult to
catch on time of Engine trouble
CAM POSITION SENSOR-2
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1. Find and connect the Signal and Ground line referencing the wiring
diagram.
2. After measuring the Signal, Compare the measured signal with Normal
Signal.
(1) Find the Rising point and Falling point of Cam signal through the tooth
counts of crank angle signal.
(2) Calculate the high and low level of cam signal as the crank angle sensor
signal’s tooth counts.
3. Check if Operating of Related components with this signal are Normal
through checking with the normal condition value of components.
< Related components >
1. Injector Timing and working status.
2. Ignition timing and working status
CAM POSITION SENSOR-3
WAVE ANALYSIS
• Magnetic type
•
Sensor signal voltage is as following graph.
CAM POSITION SENSOR-4
< Reference >
The high and low phase change of Cam signal must be generated before long
tooth of the crank signal that is at least 3 short teeth before.
CAM POSITION SENSOR-5
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WAVE ANALYSIS-Optical type
This is an optical sensor. During round plate (It is called target wheel) that has
holes is revolved with camshaft, the light is shone. If the light passes through
the hole, out put voltage is generated. This sensor uses this principle and need
power to be operated.
CAM POSITION SENSOR-6
• The level change (Edge: from high to low level/ from low to high level)
of the camshaft signal must be occurred at least two short teeth
before from the long tooth.
• If the level change of the camshaft signal is occurred at long tooth or at
short tooth before one tooth from the long tooth, We must check pulley
(TDC) position and modify to make cam signal level change at least 2
short teeth before from the long tooth.
CAM POSITION SENSOR-7
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WAVE ANALYSIS-Hall type
This one is hall type sensor and circuit
is included within sensor and 12V
power is supplied. If metal is passed
the sensing part within 1.0±0.5mm
gap, 5V (someone is 12V) output
voltage is generated through sensor
internal circuit.
CAM POSITION SENSOR-8
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The level change (Edge: from high to low level/ from low to high level) of the
camshaft signal must be occurred at least two short teeth before from the
long tooth.
If the level change of the camshaft signal is occurred at long tooth or at short
tooth before one tooth from the long tooth, We must check pulley (TDC)
position and modify to make cam signal level change at least 2 short teeth
before from the long tooth.
CAM POSITION SENSOR-9
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FIELD EXAMPLE
Vehicle : Avante 1.5L DOHC, Odometer : 48,000Km
Problem description : When acceleration during driving, the
performance is lack. And trouble code of camshaft angle sensor is
detected at times.
Cause : The trouble of camshaft angle sensor is due to no change of
polarity between two validated long tooth. The acceleration
performance is lack because camshaft sensor is assembled with
6[CRK] retard.
Signal measurement
CAM POSITION SENSOR-10
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Explanation : In case that ignition timing is controlled by ECU,
crankshaft and camshaft signal should exactly synchronized. Check the
problem after comparing with normal crankshaft and camshaft signal.
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Enlargement of application : If camshaft edge is close to long tooth
detection point, it means that ignition timing is retarded. So,
performance is decreased. If it is opposite case, it means that ignition is
advanced and it results in knocking, lack of performance and engine
damage.
TPS-1
CHECK METHOD
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NOTICE : To measure the signal, ground line
should be earth to chassis or engine
1. Check the Signal voltage with
connecting the Oscilloscope.
2. After connecting the Hi-scan,
Check that HI-scan detected the
Idling state without stepping on the
accelerator pedal.
<Connecting Method>
To measuring the Noise and
Resistance throughout TPS wiring
line exactly, That must be measured
on not Connector side but closest
position to ECU (within 30mm).
- TPS Signal line, TPS Ground line
TPS-2
1. Find and connect the Signal and Ground line referencing the wiring diagram.
2. After measuring the signal, compare the measured signal with Normal
signal.
(1) After checking in IDLE state, Measuring the signal at WOT (Whole Open
Throttle) as stepping on the accelerator pedal.
(2) It prefers to check the Air mass flow signal in the same time if possible.
< Checking item >
(1) Check that IDLE state is well recognized through the Scanner.
(2) Check that TPS signal value changed exactly according to Throttle
variation.
(3) Check that TPS adaptation value is learnt well in IDLE state.
TPS-3
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WAVE ANALYSIS
Check the output voltage according to the pedal opening degree.
< Spec. : Specification which used during development period >
TPS-4
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< Measurement : Measure the mass air flow and TPS during full acceleration
from idle>
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ECU recognized TPS signal check is essential. Through the scanner, TPS
value vs. TPS adapted value check is required during idle. If TPS value is
bigger (around 1.2) than adapted value, engine idle can be unstable due to
ECU not recognized idle status.
TPS-5
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FIELD EXAMPLE
< Example 1 > The problem by noise
Vehicle : Matiz, Odometer : 4,800Km
Problem description : RPM cycling is sometimes taken place in idle state
with engine vibration. And a lot of CO emission(1.7%) comes from exhaust
gas in idle state.
Cause : RPM cycling is taken place because ECU doesn’t recognize idle
state by noise detection of TPS signal. Whenever noise is detected, ECU
recognizes it as working rapidly acceleration pedal. And it is cause of rich
injection control as adding fuel correction when acceleration
< Rich injection control by fuel correction when acceleration >
< Amplification of noise signal : ECU doesn’t recognize idle state >
TPS-6
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Explanation : The noise is not occurred after separating TPS signal
line from TCU connecting. But if it is TPS signal line which must be
used with TCU connecting, noise may be reduced as separating TCU
from connecting part as far as possible.
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Enlargement of application : If noise is occurred in TPS signal, find
what is connected with TPS signal and ground line. And check noise
after separating it. If noise is reduced, remove connecting part. But if
removal is impossible, find point that the lowest noise is detected as
moving connecting part. Nevertheless, if noise is not decreased, find
point that the lowest noise is detected as moving ground line and
connect it. It may be implemented by shield line.
TPS-7
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< Example 2 > Micro cut-off occurrence
Vehicle : Accent 1.3 & 1.5L SOHC (Siemens system), Odometer :
Don’t care
Problem description : Sometimes engine is rough idle state. The
floating is occurred without idle recovery and surging is taken place
when acceleration. TPS value that is measured from scanner is normal
but TPS value is very small in idle state.
NOTICE : Absolutely TPS value in idle state >>> Adapted TPS value in
idle state
Cause : TPS signal is cut for very short time( 40 –120usec ). ECU
regard it as TPS value (Below 0.05volt) that is measured with micro
cut-off phenomenon in idle state(If the idle TPS value which is
memorized in ECU is less than normal one, it is set to idle TPS value).
After that if it is again returned normal, ECU recognize it as working
acceleration pedal and also don’t apply idle correction.
TPS-8
Signal measurement
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Explanation : Finally, ECU doesn’t detect idle in spite of real idle state.
So, it led to rough idle. The current vehicle (Production after Jun.1996
model year) have no problem with micro cut-off (Duration is less than
0.8) because ECU change TPS value after elapsed 0.8 [sec] in case
that current TPS value is less than memorized one.
Enlargement of application : If engine is rough idle, first compare
“absolutely TPS value” with “TPS adaptation value” from scanner in idle
state. If these two values have difference more than 1.2 [TPS], ECU
doesn’t detect idle in spite of real idle state. So, you must find root
cause after inspecting why this phenomenon is happened.
Example : Micro cut-off / Bad return of acceleration cable / Bad
connection of ground line.
TPS-9
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< Example 3 > The bad connection of TPS ground line
Vehicle : Rio 1.5L DOHC, Odometer : 3,200Km
Problem description : Sometimes engine is rough idle state. The
floating is occurred without idle recovery and severe RPM cycling is
taken place with electric load or A/C ON.
Cause : If engine becomes so hot, TPS signal is unstable in idle state
by bad connection around fuse box. So, ECU doesn’t recognize idle
state because the unstable signal is higher than “TPS adaptation value
in idle”. It results in rough idle.
Signal measurement
TPS-10
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Explanation : If RPM is unstable, the system which recognize idle by
TPS signal(Without idle switch type) should check whether ECU
recognize idle or not.
Enlargement of application : If engine is rough idle, first compare
“absolutely TPS value” with “TPS adaptation value” from scanner in idle
state. If these two values have difference more than 1.2 [TPS], ECU
doesn’t detect idle in spite of real idle state. So, you must find root
cause after inspecting why this phenomenon is happened.
Example : Micro cut-off / Bad return of acceleration cable / bad
connection of TPS ground line.
AIR FLOW SENSOR-1 CHECK METHOD
1. With connecting the
oscilloscope.
2. Check what the signal
voltage is as stepping on
and off the accelerator
pedal in idle state.
NOTICE : To measure the signal, ground line should be
earth to chassis or engine.
AIR FLOW SENSOR-2
1. Find and connect the Signal and Ground line referencing the wiring diagram.
2. After measuring the signal, compare the measured signal with Normal signal.
(1) After checking in IDLE state, Measuring the signal at WOT (Whole Open
Throttle) as stepping on the accelerator pedal
(2) It prefers to check the TPS (Throttle Position Sensor) in the same time if
possible.
3. Check the followings with connecting the scanner after making the engine fully
warmed-up and keeping Idling above 10 minutes.
< Checking items>
(1) Check that the additive adaptation value (fuel adaptation in IDLE) is in
normal range (within ±0.8 msec).
(2) Check whether the mass air flow value is changed as stepping on the
accelerator pedal.
(3) Check that the multiplicative adaptation is in normal range (within ±15%)
after driving (over 3 days)
AIR FLOW SENSOR-3 WAVE ANALYSIS
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MAP sensor
The output voltage of MAP sensor according to the pressure of surge tank is as
follows.
AIR FLOW SENSOR-4
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Hot film / Hot wire type mass air flow sensor
The output voltage of MAF sensor according to the mass air flow(Kg/Hr) is as
follows.
AIR FLOW SENSOR-5
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Karman vortex type
The output pulse is different from mass air flow.
AIR FLOW SENSOR-6 FIELD EXAMPLE
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< Example 1 > In case of misfire occurrence from engine
Vehicle : MAP sensor equipped vehicle (SOHC engine is more severe
=> Misfire is often occurred with a little bit lean fuel control)
Problem description : The unstable RPM cycling(recovery after fast
drop of RPM) and engine vibration are occurred in idle state. At the
moment MAP sensor signal show spike phenomenon (Fast jump and
drop of MAP sensor signal).
Cause : Misfire was occurred inside combustion chamber due to
instantaneous lean fuel control(SOHC is over A/F 15.3 and DOHC is
over A/F 15.7) with lean fuel correction(ECU decrease injection time
because O2 sensor voltage is over 0.5 [volt]) of O2 sensor feedback
Signal measurement
AIR FLOW SENSOR-7
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Explanation : If misfire is occurred from engine, piston speed is rapidly
reduced. At the moment the mass air flow is rapidly decreased from
surge tank and pressure inside surge tank is rapidly increased. So,
MAP sensor signal is increased as jumping.
Enlargement of application : The pressure variation inside surge tank
is related to piston speed. Without fuel supply, pressure inside surge
tank is inverse proportion to piston speed. Indeed, if piston speed is
fast pressure is low, if it is slow pressure is high. So, you can guess
compression ratio through the fact.
If pressure inside surge tank is high when dry cranking(Cranking
without fuel supply), piston speed is low and also it mean that
compression ratio is high. In the contrary, if pressure inside surge tank
is low, piston speed is high and also it mean that compression ration is
low. Therefore The compression ratio can be relatively compared by
surge tank pressure from dry cranking.
AIR FLOW SENSOR-8
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< Example 2 > In case of pulsation detection
Vehicle : MAF(Mass Air Flow equipped vehicle)
Problem description : If acceleration pedal is worked over 50% around 1300
~ 1800 RPM, MAF sensor read abruptly a lot of mass air flow value. According
to vehicle, engine may be no problem with the phenomenon but some vehicle
may have surging and fuel smell from exhaust gas due to over injection time.
Cause : The pulsation is detected in intake air line. It is due to vibration(the
front and rear direction) of air around sensing part. At the moment, if ECU
detect pulsation engine is no problem but if not ECU inject fuel as lots MAF
value. It led to rich fuel control.
Signal measurement
AIR FLOW SENSOR-9
• Explanation : The vehicle which is equipped MAF sensor don’t
calculate injection time in pulsation area and use MAF value that
is set by test with TPS & RPM. But some vehicles don’t make
input value because it may not be exact.
• The MAF sensor pulsation value has big deviation according to
car maker and especially in case of B maker, MAF sensor
voltage is measured about 4.6 [volt] when pulsation detection.
• Enlargement of application : Even though a lot of MAF signal
is detected, if engine is no problem, it may be ignored. Engine is
no problem if ECU normally control it even wrong MAF signal.
This case is example for it.
AIR FLOW SENSOR-10
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< Example 3 > The trouble check of MAP sensor signal
Vehicle : New sephia / Avella 1.3L / Pride
Problem description : Engine is stopped soon after starting. The MAP
signal is not measured. The MAP sensor signal line is broken but the
scanner detects that MAP sensor is normal.
Cause : ECU didn’t detect malfunction of MAP sensor. For detecting
malfunction of MAP sensor, MAP signal should be remained over
30[sec] less than 0.1 [volt]. But engine was stopped soon (less than
30[sec]) after starting and it didn’t satisfy malfunction detection
condition.
Signal measurement : Omission (Constant 0.07 volt )
AIR FLOW SENSOR-11
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Explanation
Above chart describe that ECU detect malfunction after elapsed 8 [sec] but
above problem vehicles detect malfunction after elapsed 30[sec]. Therefore
ECU detect malfunction after elapsed 30[sec] with “KEY ON”.
Enlargement of application : The scanner can detect it that ECU must
recognize malfunction. Therefore if ECU don’t detect malfunction, error will not
be visible through scanner. If scanner don’t detect malfunction in spite of
engine problem, it should be repaired.
AIR FLOW SENSOR-12
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< Example 4 > The problem when exhaust gas pressure is increased
Vehicle : Prince 2.0L SOHC, Odometer : about 128,000Km
Problem description : The vehicle which is equipped with MAP sensor was not
accelerated with lack of power and stalled on heavy rain day. After that engine is
hard to start and O2 sensor recognize rich fuel control. But any error is not
detected in scanner.
Assumption :
“ O2 sensor recognize rich fuel control(signal is close to 1[volt])” Through this
phenomenon, we can guess factors that control toward rich direction. It is
guessed over EMS system.
1) High pressure of fuel pump
2) Abnormal O2 sensor signal. In case of becoming damp in connecting part, it
may result in short to battery and it may lead to rich side injection control(O2
sensor signal is over 1 [volt])
3) A lot of fuel vapor gas comes from canister solenoid valve
4) The fuel adaptation value is too high with positive value. It lead to rich fuel
control before O2 sensor feedback.
5) A lot of oil gas comes from PCV valve.
6) The injection is increased by abnormally high MAF value.
7)The injection time correction is a lot due to limp home by coolant temperature
sensor trouble(Limp home mode : Called “Safe mode” and it is replace value
when malfunction)
8) The injection time is calculated too much due to limp home by air temperature
sensor trouble.
9) The injection is controlled with rich correction due to lack of mass air flow. The
lack of MAF is due to insufficient intake valve opening by hydro tappet
malfunction.
AIR FLOW SENSOR-13
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In “1)” case, if pressure of fuel
pump is high, injection time will
be controlled toward rich direction.
Why power is lack and poor
acceleration is happened during
driving? You will not be able to
answer about this problem if you
don’t have experience that check
it as changing fuel pressure. But
you can think that over injection
time control make lack of power.
•
For your reference, LBT(Leanest
Fuel Best Torque) is injection time
which is determined for best
power & torque withoutnO2
sensor feedback.
•In conclusion for “1)“, the answer is no. Because torque & power is not decreased
dramatically by over injection time control as described above charts. Actually you
can feel lack of power little bit with 20% injection time increment but don’t decrease
dramatically.
AIR FLOW SENSOR-14
•
•
•
•
If it is “2)”case, ECU will reduce injection correction as recognizing rich
control. In the case, power may be actually lack due to insufficient fuel
and it can be occurred with O2sensor feedback. So, the phenomena is
unrelated to engine start because start or post start injection time is
controlled without feedback by set value in ECU.
If it is “3)“, how to be controlled engine?
The overflow of vapor gas is determined by vapor pressure in fuel tank.
If canister solenoid valve has leakage when engine start with hot
ambient condition or idle sate, engine is roughly started and engine
stall may be occurred in idle sate. But due to that, don’t feel lack of
power and also driving about 10 [min] reduces overflow of vapor gas.
In “4)” case, it is disappeared with feedback control. Therefore this is
not major cause.
AIR FLOW SENSOR-15
•
In “5)” case, power will
not be decreased by
overflow of oil gas. Of
course, if vapor gas is
not supplied constantly
to individual cylinder,
engine vibration is
occurred and engine
sound is rough due to
A/F difference each
cylinder.
At
the
moment, O2 sensor
signal is unstable but
engine is not hard to
start.
In “6)” case, injection time will be rich before O2 sensor feedback but it is reduced
by injection time correction. So, it is not the root cause. Especially injection time is
determined by cranking conditions (Coolant temperature, RPM when cranking,
Cranking time…) without relation MAF value.
AIR FLOW SENSOR-16
•
If it is “7)” case,
measure
air
temperature
sensor.
And if TIA is less than
20 [C], set to current
TIA and if TIA is higher
than 20 [C], set to 20
[C]
coolant
temperature
.
If
malfunction of coolant
temperature sensor is
detected, cooling fan is
always ON and engine
is hard to start due to
limp
home(ECU
recognize 80[C] as
20[C].)
•If poor acceleration is occurred when first driving right after engine start and it
come back normal state after elapsed some time, it would be root cause of problem
but it is not because power is not increased after elapsed some time. ECU must
detect malfunction for limp home. But it is not the cause because any error is not
detected.
AIR FLOW SENSOR-17
•
•
•
•
•
•
•
In “8)” case, same as “7)” case. ECU recognize 20 [C] if malfunction
is detected.
<Reference> In latest algorithm, ECU recognize TIA as –5~5[C] in
case that coolant temperature is less than 10[C].
Finally, in “9)” case, rich fuel control is disappeared with feedback and
power is decreased due to lack of mass air flow. But is it impossible to
start engine due to insufficient oil supply? Of course it depends on oil
quantity in tappet but you will have experience that engine is hard to
start after assembling tappet. This may be very approached to
conclusion because power is decreased and engine is not started with
more severe case.
But we have to find key point.
In case of insufficient opening of tappet, O2 sensor signal is unstable.
And it is due to A/F difference of each cylinder by inconstant air supply
into individual cylinder. Please refer to picture for “5)”
Cause : The problem was solved from unexpected phenomena.
It is due to blocking of exhaust pipe (Blocking of exhaust pipe =>
Increase of exhaust resistance => a lot of residual gas generation =>
Increase MAP value => Over injection time => Rich fuel control => Lack
of power during driving).
OXYGEN SENSOR-1
•
CHECK METHOD
Oxygen sensor signal voltage (between 0 to 5volt) can be going well to be
heated by exhaust gas (over370degC) though Oxygen sensor has heater. And
you can diagnose the function of oxygen sensor exactly to be feedback. Check
the troubles as following procedure.
1. Keep on stepping on the accelerator pedal lasting the engine revolution over
2000rpm during 2 minutes.
2. Make the Oxygen sensor feedback: If heater was not installed, Feedback
condition is difficult at vehicle stop. Thus must drive over 5 minutes in speed
over 60Km/H generally.
< NOTICE > After making the feedback, signal must be checked on condition
of engine running not key off.
3. Measure the Oxygen sensor signal with connecting the HI-Scan or
Oscilloscope.
< NOTICE > It prefers not to use Multi-meter because it is difficult to show
the fast signal changing.
< NOTICE > In case of connecting the Auto Scanner, there is no need
additional trouble checking because It analyses and diagnoses the troubles
automatically.
OXYGEN SENSOR-2
1. Find and connect the signal and ground line with referencing the wiring diagram.
2. After measuring the signal, compare the measured signal with Normal signal.
(1) Check whether the signal switches (up and down) too fast (within 0.1 second) or
slow (over 5 second)
(2) It prefers to use the Scanner in the same time.
3. Check the followings with connecting the scanner after making the engine fully
warmed-up and keeping Idling above 10 minutes.
< Checking items>
(1) check that the additive adaptation value (fuel adaptation in IDLE) is in normal
range( within ±0.8 mmsec)
(2) check that the multiplicative adaptation is in normal range(within ±15%) after
driving( over 3 days)
OXYGEN SENSOR-3
•
•
WAVE ANALYSIS
Explanation is for zirconium O2 sensor. In case of Titanium O2 sensor, the
voltage range is 0~5V and signal is opposition.
When oxygen sensor signal is measured, the output voltage depends on
exhaust gas temperature even though heater is existed. That is, the higher
exhaust gas temperature is the higher oxygen sensor output voltage. So O2
sensor signal check should be done after acceleration. And if signal is
moving(up/down), the sensor status is considering as normal and then it’s
required the analysis of fuel delivery system of combustion chamber.
The output voltage of oxygen sensor is as follows.
<Oxygen sensor signal voltage : Zirconium(left), Titanium(right) >
OXYGEN SENSOR-4
< Too rich fuel (left) / Too lean fuel(right) >
If cylinder fuel distribution is bad,
the signal shape is unstable(fast
switching). It means sensor is
normal but fuel system is
somewhere wrong.
< In case fuel distribution is not good>
OXYGEN SENSOR-5
•
•
•
•
FIELD EXAMPLE
< Example 1 > The problem occurrence when start feedback
before O2 sensor light-off
Vehicles : New sephia 1.5L SOHC/DOHC, Odometer : More than
28,000Km Prince 2.0L SOHC, Odometer : 67,000Km Espero 2.0L
SOHC/DOHC, Odometer : 82,000Km.
Problem description : The acceleration is poor and RPM cycling is
occurred in idle state. Engine stall is happened when working rapidly
acceleration pedal with RPM cycling and if acceleration pedal is slowly
worked, RPM is slowly increased and color of exhaust gas is black.
Cause : In case of non-heated O2 sensor type, ECU control fuel
injection as starting feedback through O2 sensor before O2 sensor
light-off. At the moment, O2 sensor signal stay from 0.40 to 0.47 [volt]
because it is not reached light-off temperature, so ECU recognize lean
fuel control and add injection time. It lead to too rich fuel control(A/F = 6
~ 9) problem.
OXYGEN SENSOR-6
Signal measurement
•
•
•
Explanation : This is happened by low exhaust gas temperature. Most
of conventional vehicle, exhaust gas temperature is within from 280 to
340℃ range in idle state. Therefore it is due to low exhaust gas
temperature (Minimum temperature for O2 sensor light-off : 370℃).
Enlargement of application : Even though this problem is not
occurred with heated O2 sensor type, after replacing it, O2 sensor
signal & ground line make originally connection with ECU and heater
line connect with after main relay. After that replace new spark plug.
Reference : Fuel wetting of spark plug result in low ignition
performance.
OXYGEN SENSOR-7
•
•
•
< Example 2 > The problem occurrence due to abnormal O2
sensor signal
Vehicles : Avante 1.5L DOHC, Odometer : About 28,000Km
Problem description : Engine stall is occurred after severe RPM
cycling as soon as engine start.(As soon as O2 sensor feedback start).
At the moment, O2 sensor signal voltage stay 1.0 ~ 1.2 [volt].
Cause : O2 sensor signal
line is short to battery due
to moisture between
connecting parts. Due to
that, signal voltage is high
and ECU reduce fuel
injection(Max:33 or 50%)
as starting feedback.
Finally engine stall was
occurred with lack of fuel.
Signal measurement
OXYGEN SENSOR-8
•
•
Explanation : ECU detect malfunction of O2 sensor with signal voltage
higher than 1.3 [volt]. Therefore this case is due to feedback without
error detection.
Enlargement of application : Fuel control status that is supplied into
engine is observed by O2 sensor signal measuring but fuel injection
time adding(higher than 0.5volt) or deduction(less than 0.5volt) is only
observed. In this case, although O2 sensor signal is high due to short
to battery, we cannot distinguish whether actual fuel injection is much
or less. But you have to expect that ECU reduce fuel injection with O2
sensor feedback.
OXYGEN SENSOR-9
•
•
•
•
< Example 3 > Fuel injection status check through O2 sensor
Vehicles : Rio 1.5L DOHC, Odometer : 4,200Km
Problem description : O2 sensor signal is rapidly switched and engine
vibration is occurred. Due to knocking detection, performance and fuel
economy is poor.
Cause : The intake valve closing and opening was not exact due to
number 3 cylinder hydro tappet trouble. It result in lack of mass air flow
in corresponding cylinder and A/F of 3 cylinder is rich
Signal measurement
OXYGEN SENSOR-10
•
•
Explanation : A/F between each cylinders is different(3 cylinder is rich),
so engine vibration is occurred and ignition is retarded with knocking
detection. It leads to bad performance and fuel economy.
Enlargement of application : Fuel control status that is supplied into
engine is observed by O2 sensor signal measuring. Thus you can
estimate that fuel injection time is lack(higher than 0.5volt) or over(less
than 0.5volt). With rapidly O2 sensor signal switching, you can estimate
“fuel status that is supplied into combustion chamber” (Ex: Misfire in
combustion chamber, A/F difference between cylinders : injector
clogging, fuel gas overflow from purge valve).
INJECTOR-1
•
CHECK METHOD
1. Oscilloscope
2. Wiring diagram of injector.
< Reference >
It prefers not to use Multi-meter because it is difficult for the Multi-meter to
display the fast signal changing.
1. Find and connect the signal and ground line with referencing the wiring
diagram.
2. After measuring the signal, compare the measured signal with Normal
signal.
(1) Is the injector opening point different at each cylinder?.
(2) Is the injector opening point different at each cycle?.
(3) Is the injector opening voltage normal at each cylinder?
3. It prefers to check the following signals at the same time to check the
normal operating state of injector exactly.
< Checking items>
(1) Crank angle sensor signal: Opening point.
(2) Oxygen sensor signal: Is the oxygen sensor signal switching (Up and
down) frequency constant, too fast switching and noising of oxygen sensor
signal: there is some injector defect (opening defect, injector clog)
INJECTOR-2
INJECTOR-3
•
WAVE ANALYSIS
Output voltage when injector is operating.
INJECTOR-4
•
Injector signal with crank angle position signal .
INJECTOR-5
•
•
•
•
FIELD EXAMPLE
< Example 1 >
Vehicle : Tiburon 2.0L DOHC, Odometer : 78,000Km
Problem description : RPM increase is too slow when acceleration and
surging is occurred during driving. O2 sensor signal is very unstable.
Cause : O-ring is torn when insert injector. And fuel line has leakage from
the point. It results in inconsistent fuel supply into combustion chamber.
Signal measurement
INJECTOR-6
•
•
•
•
•
•
Explanation : In case of malfunction of injector itself(Clogging, Trouble
of internal coil), injector signal is similar to normal. Therefore it is so
difficult to find malfunction of injector with injector signal and the
problem should be solved with A/F of individual cylinder from O2 sensor.
Enlargement of application : When O2 sensor signal is unstable, you
should expect that A/F is different between cylinders and find the root
cause.
Reference : Cause type
(1) The overflow of fuel gas from PCV or purge valve
(2) Insufficient fuel supply from a certain injector
(3) The lack of mass air flow from a certain cylinder (Abnormal
closing and opening of intake valve)
INJECTOR-7
•
•
•
Vehicles : Avella / New sephia / Pride
Problem description : Engine is started with hesitation. Engine is
stopped soon after started in cold ambient condition and restart is hard.
Cause : Power, which is supplied, to distributor is cut during very short
time when key is released after engine start. This phenomenon cause
abnormal crank angle signal and it result in engine problem. Injector
signal is intermittently missed.
Signal measurement
INJECTOR-8
•
•
•
•
•
•
•
•
Explanation : When key is released after engine start, ECU stop fuel
injection from long tooth detection as soon as missing crank angle
signal by the bouncing phenomenon(Repeat contact and non-contact)
and start again injection after normal long tooth signal is detected..
Enlargement of application :
In case of fuel injection stop or abnormal ignition timing, ECU doesn’t
acquire normal crank angle signal, so crank angle sensor signal should
be checked whether it is normal or not. And ignition timing and fuel
injection control should be checked at the same time.
The cause of these cases is guessed as followings
A. In case of back-fire of LPG vehicle
B. In case that engine stall is suddenly occurred in idle sate
C. In case that engine vibration is intermittently occurred
D. In case that engine is started with hesitating as jamming flywheel in
self motor
IGNITION-1 CHECK METHOD
1. Oscilloscope (2nd Order signal measuring instrument)
2. Wiring diagram for ignition.
< NOTICE>
It prefers not to use Multimeter because it is difficult to display the fast
changing signal.
1. Find and connect the signal and ground line with referencing the wiring
diagram.
2. After measuring the signal, compare the measured signal with Normal
signal.
(1) Dwell time / ignition timing at each Coil.
(2) Signal wave showed at each coil. (2nd order wave if possible)
3. It prefers to check the following signals at the same time to check the
normal operating state of injector exactly.
< Checking items >
(1) Cam and Crank angle signal: check the abnormal ignition timing.
(2) Oxygen sensor signal: Is the oxygen sensor signal switching (Up and down)
frequency constant, too fast switching and noising of oxygen sensor signal:
phenomenon by Misfire.
IGNITION-2
•
IGNITION-3
Wave Analysis
Voltage shape during ignition is as shown below
IGNITION-4
•
•
•
•
•
•
•
•
•
Ignition Primary signal check
Ignition secondary wave shows discharging status according to the status of the cylinder.
As it has a complex relation with status of components and wires which control electrical
energy at first coil, status of second coil which is induced by high voltage and status of
mixed gas in the cylinders representing how much thermal electrons discharge while being
discharged finally, To confirm whether status of supplying electrical energy to ignition
system is good or not, it is desirable to check the current from first coil at each cylinder.
To generate enough ignition energy at secondary voltage, there must be enough current at
first coil. Although this current is different according to the sorts of the vehicle, generally
6±0.5A is considered as a standard.
The point keeping in mind is despite this current is weak, ignition secondary wave may not
have any problem.
If air-fuel ratio in the normal temperature (over 20 °C) is closer to stoichiometric , Ignition
by secondary voltage is possible with approximately 1/200~1/1000 energy of the ignition
energy in the cold temperature (below -5°C).
In case that the current flows weak , but ignition secondary wave has no problem,
Ignition secondary wave must be confirmed whether it is normal state at rapid acceleration,
cold temperature, both rich and lean of fuel condition.
Ignition energy at normal temperature and stoichiometric condition : 1~2mJ
Cold temperature and Rich fuel: approximately 1J
IGNITION-5
1) Distributor Less Ignition type
< Measuring part>
Measure flowing time and the current at checkpoint 1,2
<Checkpoint>
Resistance of wire, status of components (checking components 1: internal ECU
or external TR)
IGNITION-6
2) Distributor Ignition type
<Measuring part>
Measure flowing time and the current at checkpoint 1,2
<Checkpoint>
Resistance of wire or a short, status of components (checking components 1:
internal ECU or External TR, checking components 2: ignition coil)
IGNITION-7
•
Most important point is dwell time(depends on battery voltage). If battery
voltage is 13.5V the dwell time is 3.0~3.5msec. Cylinder by cylinder
deviation(over 20%) check is required to know the normal or not. If the
deviation is more than 20%, it means coil, power TR or wire has a problem..
•
Also check the ECU recognized battery voltage is stable(within 3V). Because
the dwell time can be some difference depends on battery voltage.
IGNITION-8
IGNITION-9
•
•
•
•
•
•
•
Ignition Primary signal check
Ignition secondary wave means discharging to high voltage from electric
energy at first coil. Especially ignition system in automobile, discharging time
& discharging voltage level is affected more by status of the mixed gas in the
cylinders and plug than electric energy from first coil.
When secondary high voltage (approximately 20000~30000V) is induced
instantly and flows, the flow means discharging, time is discharging time,
Voltage is discharging voltage.
When the secondary voltage generates, this energy separates carbon and
hydrogen from constituent of fuel.
While this constituent of fuel separates, electrons are generated. It’s called
thermal-electron.
Discharging voltage combusted normally from the cylinder is a voltage
discharging through those thermal-electrons.
Since level and time of the discharging voltage are affected by the temperature
and shape (vortex) in the cylinder, air-fuel ratio of the mixture, and
compression ratio, it is hard to fix absolute value. So it must be analyzed
through comparing each cylinder.
IGNITION-10
<Ignition secondary wave: classification of each wave>
<Ignition secondary wave: analysis graph of each wave>
IGNITION-11
•
•
•
•
•
Parts to confirm ignition secondary wave are as follows.
1) Distributorless type
<Measuring parts>
Measure flowing time and the current at checkpoint 1,2
<Checkpoint>
Resistance of wire, status of components
2) Distributor Ignition type
<Measuring part>
Measure voltage secondary wave at checkpoint 1,2(plug wire at each
cylinder)
<Checkpoint>
Resistance of wire or short, status of components (checking components 1,2)
IGNITION-12
IGNITION-13
Comparing each cylinder
(1) After a current flowed, if peak (voltage of surge) is low or discharging time is short and
high: This means that electric energy through discharged thermal-electron isn’t
discharging well, while molecule separates from fuel.
Electric energy trying to ignite isn’t for fuel combustion , it’s kind of discharging
phenomenon through plug ejja. So misfire occurs in the cylinder.
a.
Confirm the status of plug (attached carbon, clearance)
When a peak voltage is generated, some parts of voltages flow on the attached
carbon in the plug tip. So it gets weak to separate molecule.
In case that discharging voltage flows through carbon to plug ejja.
b. Check plug wiring and status of coil
In case that connection to plug and high voltage wire and coil status aren’t good ,
peak voltage becomes weak.
Then electric energy to separate fuel molecule becomes weak because Thermalelectrons generated from fuel are little so that resistance discharges large state..
c. Check if the mixture ratio of fuel is too lean
In case that fuel is lean, even more electric energy is needed to generate thermalElectrons separated from fuel molecule, Thus peak voltage generated near
stoichiometric with normal fuel isn’t enough to generate thermal-electron so that
resistance discharge large state
IGNITION-14
d. Check if the compression ratio is too high
In case compression is high, far more electric energy is needed to generate
thermal-electrons separated from fuel molecules.
Thus peak voltage generated near normal compression ratio isn’t enough to
generate thermal-electron so that resistance discharges large state. -- It isn’t for
normal case.
it’s for especially reorganized vehicle. Just do interpret that as theoretical
aspect.
<Reference>
More detail refers to chap 6. “6.3 uniform ignition energy to each cylinder
IGNITION-15
•
•
•
(2)After a current flowed, if a peak(voltage of surge) is low and discharging
time is long:
Although electric discharge is well, it causes power reduction because
discharging electric energy (spark) gets weak and long so that combustion
timing of fuel gets long and flame spread leading to combust between fuel
particles gets weak
a. Check status of plug (clearance of tip is too small)
b. Check compression pressure of cylinder is low
c. Check the mixture ratio is too rich
<Reference>
More detail refers to chap 6.”6.3 uniform ignition energy to each cylinder.
IGNITION-16
IGNITION-17
IGNITION-18
FIELD EXAMPLE
< Example 1 >
Vehicles : Tiburon 2.0L DOHC, Odometer 42,000Km
Problem description : The vehicle which platinum plug is equipped has
poor performance when acceleration, black color of exhaust gas and engine
is hard to start in cold ambient condition.
Cause : There was no problem in platinum spark plug but plug that is used
in high temperature condition(For racing car) was equipped. Therefore it led
to insufficient secondary ignition fire with too low tip temperature.
Signal measurement : In case of using all of platinum spark plug,
secondary ignition signal is normal. But it has big difference after replacing
original plug(Heat value No.7).
IGNITION-19
IGNITION-20
•
•
•
•
•
•
•
Explanation (Analogical interpretation) : The resistance is low
because tip is not heated easily with platinum plug of cooling type. So,
peak voltage is circulated into plug tip before discharging heat electron
from fuel and discharge voltage is a little bit high because resistance of
tip is bigger than discharging through a electron from fuel.
Enlargement of application : If the discharge voltage is high with
short duration, it is not discharged by heat electron that is discharged
from fuel. It is discharged into other part and lead to insufficient ignition
fire.
A. The carbon accumulation of plug tip
B. Too lean fuel control
C. Ignition coil line is open circuit or peak voltage is low due to bad
ignition coil
D. The gap of plug tip is too wide
E. Insufficient secondary voltage due to bad ignition coil
IGNITION-21
•
•
•
•
•
< Example 2 >
Vehicle : Scoupe alpha 1.5L Turbo, Odometer : 128,000Km
Problem description : Engine is stopped with starting and restart is
hard. After elapsed long time, engine is started but stopped soon.
Cause : The spark plug has no resistance. After discharging as using it,
big noise is happened and influence to ECU. It makes a mistake in
ECU.
Signal measurement : After discharging, oscillation of ignition signal is
big and long comparing to normal. It has big difference comparing to
plug of other cylinder
IGNITION-22
IGNITION-23
•
•
•
•
•
•
Explanation : The secondary ignition is factor to generate the biggest
noise in vehicle. This example prevents normal operation of ECU. But it
also may make noise into other component and actuator for electronic
control.
Enlargement of application : If you accumulate many experiences for
discharging voltage signal, you can get criteria for normal ignition signal.
If ignition signal has big difference comparing to normal. find normal
discharging voltage signal as changing factor with the experience.
A. Spark plug (For racing car, Heat value, To be resistance or not, Gap,
Carbon accumulation Etc.)
B. Wiring for high tension voltage of ignition system
C. Parts of ignition system (Coil, Power TR Etc.)
D. Injector (Flow for tuning, Spray angle, number of injector nozzle Etc)
E. Abnormal fuel (Overflow of fuel gas through PCV or purge valve) or
overflow of EGR gas
IGNITION-24
•
•
•
•
•
< Example 3 >
Vehicle : Avante 1.5L DOHC, Odometer : 86,000Km
Problem description : RPM is unstable in idle state after engine start.
Engine vibration is also happened. The performance is lack when
acceleration.
Cause : The carbon is accumulated on stem of intake valve. The intake
valve is not closed completely with warmed up engine because valve
stem is bigger and bigger with engine warm up. It results in low
compression pressure. In case of using adding material to promote
research octane number, carbon in element of fuel is accumulated on
metal.
Signal measurement :
The secondary ignition signal of cylinder which is occurred the
phenomena has long and low discharging voltage.
IGNITION-25
IGNITION-26
•
Explanation : Low compression pressure makes low discharging
energy of secondary ignition signal. If discharging energy is low, energy
that is conducted to secondary ignition coil is completely exhausted and
need long time. Therefore discharging voltage is low and time is long.
•
Enlargement of application : The low discharging voltage mean that
resistance for discharging is low. It led to insufficient ignition fire and
hard to ignite in mixed fuel gas.
A. Spark plug (The gap of plug is too narrow)
B. Moisture in combustion chamber
C. Too low compression pressure
•
ISC VALVE-1
CHECK METHOD
1. Oscilloscope.
2. Wiring diagram of ISC valve.
< Reference>
It prefers not to use Multi-meter because it is difficult for the Multi-meter to display
the fast signal changing.
1. Find and connect the signal and ground line with referencing the wiring diagram.
2. After measuring the signal, compare the measured signal with Normal signal.
(1) As there is several power lines according to ISC valve type, Measure the
signal at the same time.
(2) Let’s reference that ISC valve power line is shorted by ECU though source
of electricity is from Battery.
(3) ISC Valve operation reiterates ON/OFF. If there is one power line, valve
Opening (%) is the value when the source of electricity is ‘0’ voltage. If in case
of Open /close type, valve opening is the value when the source of electricity of
open side is ‘0’voltage.
(4) In case of step motor type, Check with normal operation value because
there is difference of ON from OFF in opening value.
3. It prefers to check the following signals at the same time to check the normal
operating state of ISC valve exactly.
ISC VALVE-2
ISC VALVE-3
WAVE ANALYSIS
Duty type
Output voltage when ISC(idle Speed Control) is moving is as shown below
ISC VALVE-4
ISC VALVE-5
•
Finally engine speed shows quantity of air flow through ISC valve. Usually, 30
~ 50 rpm increase of engine speed by 0.39% ISC valve opening.
ISC VALVE-6
WAVEFORM
ISC VALVE-7
< Reference>
It is very difficult to find out the malfunction of ISC valve by observing ISC valve
signal.
Therefore check as followings :
(1) Check deposit in the ISC valve inside such as carbon.
(2) Too much adapted minus adaptation value of ISC valve.
Counter measure :
(1) Fixing of valve: Check with naked eyes, if there is carbon, clean it.
(2) Adaptation value: Check amount of minus value by scanner. If minus value is
too big, delete adaptation value and do adaptation again in idle for 10 minutes
until engine get warmed up.
ISC VALVE-8
Step type
Finally engine speed shows quantity of air flow through ISC valve. Usually, 30 ~
50 rpm increase of engine speed by 0.39% ISC valve opening.
ISC VALVE-9
WAVEFORM
ISC VALVE-10
< Reference>
It is very difficult to find out the malfunction of ISC valve by observing ISC
valve signal.
Therefore check as followings :
(1) Check deposit in the ISC valve inside such as carbon.
(2) Too much adapted minus adaptation value of ISC valve.
Counter measure
(1) Fixing of valve: Check with naked eyes, if there is carbon, clean it.
(2) Adaptation value: Check amount of minus value by scanner. If minus value
is too big, delete adaptation value and do adaptation again in idle for 10
minutes until engine get warmed up.
ISC VALVE-11
DC motor type
Finally engine speed shows quantity of air flow through ISC valve. Usually, 30 ~
50 rpm increase of engine speed by 0.39% ISC valve opening.
ISC VALVE-12
WAVEFORM
ISC VALVE-13
< Reference>
It is very difficult to find out the malfunction of ISC valve by observing ISC
valve signal.
Therefore check as followings :
(1) Check deposit in the ISC valve inside such as carbon.
(2) Too much adapted minus adaptation value of ISC valve.
Counter measure
(1) Fixing of valve: Check with naked eyes, if there is carbon, clean it.
(2) Adaptation value: Check amount of minus value by scanner. If minus value
is too big, delete adaptation value and do adaptation again in idle for 10
minutes until engine get warmed up.
ISC VALVE-14
•
•
•
•
•
•
FIELD EXAMPLE
< Example 1 > ISC valve stuck
Vehicle : Most of KIA vehicles(Duty control type, ISC valve quipped
vehicle), Odometer : 20,000Km
Problem description : Engine operating state doesn’t recover into idle
with floating and RPM cycling is occurred. In some case, RPM is
severely dropped or engine stall is happened with electric load.
Cause : ISC valve is stuck because pintle is not moved by carbon
accumulation. It led to impossible ISC correction.
Signal measurement : Basically it is not different with normal signal.
Even if it has difference, that is rare and it is not helpful to analyze.
Explanation : In this case, ECU adapt too much(100±40%). Thus, first
you should check adaptation value of ISC. For more detail, refer to 7.1
Duty ISC valve.
Enlargement of application : With duty control ISC valve, if the severe
engine vibration is occurred (Big RPM variation) and RPM floating or
engine stall is intermittently happened in idle, you should check ISC
valve stuck. Notice to customer that this problem is reoccurred after
healing.
ISC VALVE-15
•
•
•
•
•
< Example 2 > ISC valve step loss
Vehicle : Most of DAEWOO vehicles(Step type ISC valve equipped
vehicle), Odometer : Don’t care
Problem description : Engine operating state doesn’t recover into idle
with floating and RPM cycling is occurred. In some case, RPM is
severely dropped or engine stall is happened with electric load.
Cause : ISC valve step is not synchronized with ECU control. It led to
impossible ISC correction.
Explanation : In this case, ECU adapt too much(100±40%). Thus, first
you should check adaptation value of ISC. For more detail, refer to 7.1
Duty ISC valve.
Enlargement of application : With step type ISC valve equipped
vehicle, if the severe engine vibration is occurred (Big RPM variation)
and RPM floating or engine stall is intermittently happened in idle, you
should check ISC valve stuck. Notice to customer that this problem is
reoccurred after healing.
ISC VALVE-16
•
•
•
•
•
•
•
•
< Example 3 > The problem by too much adaptation
Vehicle : MAP sensor equipped vehicle(Most vehicle of SIEMENS
EMS system), Odometer: 6,000Km
Problem description : Engine operating state doesn’t recover into idle
with floating and RPM cycling is occurred. In some case, RPM is
severely dropped or engine stall is happened with electric load.
Cause : ISC basic opening duty is too big or small by abnormal
adaptation value. It results in abnormal total ISC correction. It makes
above described problem.
Signal measurement : The signal is normal.
Explanation : In this case, ECU adapt too much(100±40%). Thus, first
you should check adaptation value of ISC. For more detail, refer to 7.1
Duty ISC valve.
< Reference >
The MAP sensor system operates engine without problem even though
mass air flow is come from besides ISC valve. Therefore ISC valve
decreased in proportion to additional air flow and ECU adapt as
reduced ISC quantity.
ISC VALVE-17
ISC VALVE-18
Enlargement of application : With duty control ISC valve, if the severe
engine vibration is occurred (Big RPM variation) and RPM floating or engine
stall is intermittently happened in idle, you should check ISC valve stuck.
Notice to customer that this problem is reoccurred after healing.
AIR TEMPERATURE SENSOR-1
CHECK METHOD
1. Oscilloscope or Multi-meter.
2. Wiring diagram of air temperature sensor.
1. Find and connect the signal and ground line with referencing the wiring
diagram.
2. After measuring the signal, compare the measured signal with Normal
signal.
(1) Compare the current measuring signal voltage and air temperature
with that of normal condition values.
(2) Check the real air temperature with connecting the scanner.
3. It prefers to check the following items at the same time to check the
troubles of air temperature sensor exactly.
< Checking items >
(1) Air temperature value read by scanner.
AIR TEMPERATURE SENSOR-2
NOTICE : To measure the signal, ground line should be grounded to chassis or engine.
AIR TEMPERATURE SENSOR-3
WAVE ANALYSIS
•
The following graphs show sensor signal voltage by air temperature.
AIR TEMPERATURE SENSOR-4
AIR TEMPERATURE SENSOR-5
FIELD EXAMPLE
•
•
•
< Example 1 > Influence by TIA sensor trouble
Vehicle : SIEMENS / BOSCH system (TIA sensor equipped vehicle)
Problem description : The check engine lamp is illuminated but
engine has no trouble. But when take off vehicle after idling during long
time, severe knocking is happened. Especially it is more severe with
traffic jam driving.
Cause : Due to TIA sensor trouble, ECU recognize high intake air
temperature as 20℃. Thus ignition is not retarded with high intake air
temperature and it led to knocking.
AIR TEMPERATURE SENSOR-6
•
Signal measurement
: This is TIA and knock sensor signal with TIA sensor trouble and
knocking.
AIR TEMPERATURE SENSOR-7
•
•
Explanation : If intake air temperature is high, the flame propagation
velocity is short after igniting in combustion chamber. Thus, ignition
timing should be retarded with fast flame propagation velocity. The
retard value is proportioned to mass air flow increase. If TIA is
increased from 40 to 80℃, ignition should be retarded 4 ~ 6 [CRK].
Enlargement of application : If TIA sensor has trouble, correction
value by TIA is not exact.
a)In case of fuel control, O2 sensor feedback is too small or big.
b) In case of ignition control, knocking is happened with hot engine
state.
c) Adaptation value of ISC valve is too small or big.
COOLANT TEMPERATURE SENSOR-1
CHECK METHOD
1. Oscilloscope or Multi-meter
2. Wiring Diagram for Coolant temperature sensor
1.Find and connect the Signal and ground line referencing the wiring diagram.
2.After measuring the signal, compare the measured signal with Normal signal.
(1)Referencing the signal voltage and temperature in normal condition,
compare the current measuring signal and temperature with normal signal.
(2)Checking the real coolant temperature with connecting the Scanner in the same
time.
3. It would like to check the following item due to analyzing the coolant
temperature sensor exactly.
< Checking item >
(1) Coolant temperature reading through Scanner.
COOLANT TEMPERATURE SENSOR-2
COOLANT TEMPERATURE SENSOR-3
WAVE ANALYSIS
•
The following graphs show sensor signal voltage by coolant temperature
COOLANT TEMPERATURE SENSOR-4
COOLANT TEMPERATURE SENSOR-5
FIELD EXAMPLE
•
•
< Example 1 > The coolant temperature sensor signal is too less than
actual
Vehicle : Avella 1.5L DOHC, Odometer : 43,000Km
Problem description : There is no problem with first cranking but restart is
hard after driving(warmed up) and poor acceleration is happened. After
driving again, it returns normal. The overheat is occurred.
•Cause : Actual coolant
temperature is higher
than 80℃ but sensor
recognize 40 ~ 60℃.
Thus this lead to too
much injection time
correction. It is cause
the problem.
•
Signal measurement
COOLANT TEMPERATURE SENSOR-6
•
•
•
•
•
•
Explanation : The cooling fan is ON with 92℃ and OFF with 85℃. The
cooling fan is OFF due to low coolant temperature detection of TCO
sensor. Poor acceleration is occurred because fuel supply is too much
before O2 sensor feedback control. And the phenomena is cleared with
O2 sensor feedback.
Enlargement of application : Injection time correction by coolant
temperature is very big comparing to other correction factors and target
idle RPM is different with coolant temperature. Therefore, if followings
are questionable, check coolant temperature.
A.
Too much fuel supply (Especially with engine start)
B.
High idle RPM
C.
The cooling fan ON /OFF is frequently repeated.
COOLANT TEMPERATURE SENSOR-7
•
•
•
•
< Example 2 > Too fast change of TCO sensor signal
Vehicle : Rio 1.5L DOHC, Odometer : 4,000Km
Problem description : With uphill and downhill driving in GIRI Mt. Idle
RPM is repeated with high and low control. And O2 sensor feedback is
lean and knocking is occurred with fast acceleration.
Cause : It has big difference between actual coolant temperature and
sensing temperature of TCO sensor. The reason why TCO sensor is
located with fast cool down position.
•
Signal measurement
COOLANT TEMPERATURE SENSOR-8
•
•
•
•
•
Explanation : Knocking is occurred because ignition is not retarded by
TIA and TCO correction. O2 sensor lean control is to reduce fuel by too
much correction. Low coolant temperature make high Idle RPM.
Enlargement of application : Injection time correction by coolant
temperature is very big comparing to other correction factors and target
idle RPM is different with coolant temperature. Therefore, if followings
are questionable, check coolant temperature.
A.
Too much fuel supply (Especially with engine start)
B.
High idle RPM
C.
The cooling fan ON /OFF is frequently repeated.
BATTERY VOLTAGE-1
CEHCK METHOD
1. Oscilloscope (It prefers not to use Multi-meter )
2. Wiring Diagram for Battery voltage (Voltage recognized in the ECU)
3. Scanner
1. Find and connect the Signal and Ground line referencing the wiring diagram.
2. Check How is the Signal voltage with connecting the scanner.
3. After connecting the Hi-scan, Check that HI-scan detected the Idling state
without stepping on the accelerator pedal.
< NOTICE1 >
In case of connecting the Multi-meter, It is difficult to measure the variation of
voltage varying short and fast. It prefers not to use Multi-meter to checking if
there is that rapid variation of voltage.
< NOTICE2 >
In case of connecting the Auto-scanner, we can get the reference as analyzing and
diagnosing the rapid voltage variation automatically.
BATTERY VOLTAGE-2
Connecting Method: To get more exact voltage, it must be measured on not battery
side but closest position to ECU (within 30 mm)
Connection part:
(1) Battery voltage: Reference to Wiring diagram, Ground part: Battery(-)
(2) Oxygen sensor signal: if there is Checking items “(2)”phenomenon.
(3) Ignition, Injector opening : If there is Checking items”(3)”phenomenon.
Comparing Method:
After measuring the signal, Compare the measured signal with Normal signal.
(1) After checking in IDLE state, Measuring the signal at WOT (Whole Open Throttle)
as stepping on the accelerator pedal.
(2) It prefers to check the Battery voltage with connecting the Scanner in the same time.
< Checking items >
(1) Is the measured value same as that of displaying through Scanner?
(2) Is there a battery voltage variation each time?
(3) Check if Oxygen sensor signal switching ( signal UP and Down) is too fast or signal
shape is not clear When above “(2)”phenomenon appeared.: In this phenomenon,
we assumed that injector opening or ignition dwell time is unstable as voltage
recognized at ECU varying.
BATTERY VOLTAGE-3
BATTERY VOLTAGE-4
FIELD EXAMPLE
< Example 1 > Fast battery voltage change
Vehicle : Rio, Odometer : 2,400Km
Problem description : Engine vibration is severe and knocking detection is
frequent. Surging is occurred during driving.
Cause : Fast voltage
variation is happened
in line reading battery
power in ECU. ECU
calculates dwell time
with
this
irregular
voltage and it led to
unstable combustion.
Signal measurement
BATTERY VOLTAGE-5
Explanation : In case of rapidly current increment by dwell time of ignition
coil, combustion in each cylinder is unstable. The vibration that is
occurred at this time is detected as knocking and it results in bad fuel
economy and performance.
Enlargement of application : Unstable vehicle wiring prevent stable
power supply and sensor signal.
KNOCK SENSOR-1
CHECK METHOD
1.Oscilloscope (It prefers not to use Multimeter available)
2.Wiring Diagram for Knock sensor
3.Scanner
1.Find and connect the Signal and Ground line referencing the wiring diagram.
2.Connecting the Oscilloscope, check the Signal Voltage.
3.Measuring the Knock signal as making the rapid RPM change stepping on
and out the Accelerator pedal
< NOTICE1 > Knock sensor signal is very fast (about 20KHz) and like Noise
signal. Thus it prefers not to use Multimeter for checking the Signal status.
< NOTICE2> In case of connecting the Auto-scanner, we can get the reference
of the checking troubles because Auto-scanner is analyzing and diagnosing the
some troubles automatically.
KNOCK SENSOR-2
Connecting Method : To get more exact voltage, it must be measured on not
battery side but closest position to ECU(within 30 mm).
Comparing Method :Compare the measured signal with Normal signal.
(1) After checking in IDLE state, Measuring the signal at WOT(Whole Open
Throttle) as stepping on the accelerator pedal.
(2) With Connecting the Scanner, It prefers to check the ignition retard value by
Knocking when Knock signal shows big variation( ECU detected knocking).
< Checking items >
(1) Is the Spark retard value through Scanner well displayed?
: Whether Ignition spark timing is retarded when real sound of Knocking is heard
or Knock signal fluctuation is big (fluctuate between 1V and 5V).
(2) Whether the knock signal is lasted too low voltage (below 0.5 Volt) without
big variation or is fluctuated severely.
(3)Whether the Knock signal line (or Ground line) is broken,
(4) Though knocking sound is still heard with normal condition or ignition retard
is still “0” with big knock signal fluctuation, followings are assumed.
(a) Communication problem of the ECU internal: Knock signal is controlled by
the ECU.
(b) Ignition angle is set to “0” by ECU arbitrary.
KNOCK SENSOR-3
KNOCK SENSOR-4
WAVE ANALYSIS
Signal characteristic of knock sensor is as followings :
A. Voltage characteristic of knock sensor :
26± 8 mV / g ( 5KHz base)
B. Voltage linearity of knock sensor :
3 - 12 KHz : ± 15% ( 5KHz base)
12 - 20 KHz : ± 25% ( 5KHz base)
C. Electrical characteristic of knock sensor :
(1) CAPACITANCE : 0 - 1.4nF
(2) Frequency range : 3 - 20 KHz / Acceleration range : 100G
(3) Insulated resistance : Above 1MΩ with 750V
KNOCK SENSOR-5
< Knocking signal
: Without knocking(left) /
With knocking (right) >
KNOCK SENSOR-6
FIELD EXAMPLE
< Example 1 > Fast battery voltage change
Vehicle : Rio, Odometer : 2,400Km
Problem description : Engine vibration is severe and knocking detection
is frequent. Surging is occurred during driving.
Cause : Fast voltage variation is happened in line reading battery power
in ECU. ECU calculates dwell time with this irregular voltage and it led
to unstable combustion.
Signal measurement
KNOCK SENSOR-7
Explanation : In case of rapidly current increment by dwell time of ignition
coil, combustion in each cylinder is unstable. The vibration that is
occurred at this time is detected as knocking and it results in bad fuel
economy and performance.
Enlargement of application : Unstable vehicle wiring prevent stable
power supply and sensor signal.
VEHICLE SPEED SENSOR-1
CHECK METHOD
11. Oscilloscope (It prefers not to use Multi-meter )
22. Wiring diagram of vehicle speed sensor.
3. Scanner
11. Find and connect the Signal and Ground line referencing the wiring diagram.
22. Check How the Signal voltage is with connecting the Oscilloscope.
33. Because it is difficult to measure the vehicle speed on driving, make the
vehicle lock the rear wheels and lift the front wheels. And then engage the gear
and declutch. At this time, let’s reference that the vehicle speed displayed on
Meter set is half of real speed due to mechanism of differential gear.
< Reference >
In case of connecting the Multimeter, It prefers not to use multimeter because
it is difficult to measure the vehicle speed signal, which continue ON/OFF fast.
< Reference >
In case of connecting the Auto-Scanner, Let’s reference the results because
Auto-scanner diagnoses some vehicle speed signal’s troubles automatically.
VEHICLE SPEED SENSOR-2
Comparing Method: After measuring the signal, compare the measured signal with
Normal signal.
(1) Compare the current measured vehicle speed signal and frequency with that of
normal condition.
(2) It would like to check the Battery voltage with connecting the scanner if possible.
< Checking items >
(1) Whether the scanner recognizes the vehicle speed though vehicle stop.
(2) Whether the noise is occurring in the vehicle speed signal.
(3) Whether the ON/OFF level of vehicle speed signal is not changed on driving.
VEHICLE SPEED SENSOR-3
WAVE ANALYSIS
Signal characteristic of vehicle speed sensor is as followings :
Voltage characteristic of vehicle speed sensor
1. Reed switch type : 0 – 12 / 0 – 5 volt
2. Hall type : 0 - 5 / 0 – 12 volt
3. Magnetic type : 0 – 40 volt (Change by speed)
VEHICLE SPEED SENSOR-4
< Reference >
ECU and TCU recognize wrong vehicle speed by noise from vehicle speed sensor.
If noise is occurred, check whether ECU recognize vehicle speed with vehicle stop
and if it is true, remove noise.
<The cut off of vehicle speed sensor noise>
VEHICLE SPEED SENSOR-5
FIELD EXAMPLE
Vehicle : Credos 2.0L DOHC A/T, Odometer : 28,000Km
Problem description : Vehicle should be started with 2 or 3-gearshift and
acceleration performance is lack.
Cause : ECU recognize 40∼70Km/H driving with engine stop because noise is
detected with vehicle speed signal . Thus gear was shifted to 2 0r 3.
Signal measurement
VEHICLE SPEED SENSOR-6
Explanation : ECU calculate vehicle speed with only frequency(ON/OFF
pulse per second). It is not related to height and width of pulse signal.
Therefore up and down signal is recognized as pulse for vehicle speed
calculation.
Enlargement of application : In case of using pulse for vehicle speed
calculation, ECU calculate vehicle speed with only frequency(ON/OFF
pulse per second). Therefore pulse has noise, it should be counter
action.
< The signal using as input pulse signal >
A. Crank angle signal
B. Camshaft angle signal
C. Vehicle speed signal
D. Knock signal
E. Communication signal between ECU and TCU : TPS, Coolant
temperature, Engine torque, RPM, Engine torque reduction request etc.
EGR VALVE-1
1.
2.
3.
4.
CHECK METHOD
Oscilloscope ( Multi-meter should be not used for duty or EEGR type)
Wiring diagram of EGR
Scanner
Multi-meter : Only in case of ON/OFF type EGR
Comparing Method: After measuring the signal, compare the measured signal with
Normal signal.
(1) Compare the opening value ( Duty when the voltage is ‘0’) with the frequency
from normally measured signal.
(2) It would be better check the EGR operating state with connecting the Scanner..
(3) Check the EGR position sensor value.
< Check items >
(1) Is the Frequency right?
(2) Check whether the EGR valve is not opening even though operating or opening
even though not operating
(3) Is there any sensor operating voltage / Ground line broken?
<
EGR VALVE-2
< Measuring tool connection >
EGR VALVE-3
EGR valve characteristic is as followings:
1. Mechanical EGR valve
WAVE ANALYSIS
EGR VALVE-4
2) Electrical EGR valve
EGR VALVE-4
FIELD EXAMPLE
< Example 1 >
Vehicle : Sephia II 1.5L DOHC, Odometer : 24,000Km
Problem
description
:
Severe engine
vibration
is
occurred in idle
and driving is
impossible due
to engine stall.
Cause : Misfire
is happened due
to overflow of
EGR gas with
EGR valve open
stuck.
Signal measurement : EGR position sensor voltage remain 1.8[volt] after working
acceleration pedal.
EGR VALVE-5
Explanation : EGR valve stuck is often occurred. U.S export vehicle is
equipped with temperature. If low temperature is maintained with EGR
operating range, ECU recognizes closing stuck. In the contrary if high
temperature is maintained with non-operating range, ECU recognize
opening stuck.
Enlargement of application : Ignition timing and fuel injection is
calculated with considering EGR quantity in EGR operating range.
Thus, if EGR is not come into operating range, they have difference.
Oppositely, if EGR gas is come with non operated EGR, ignition has big
difference.
CANISTER PURGE VALVE-1
CHECK METHOD
1. Oscilloscope (It prefers not to use Multimeter available)
2. Wiring Diagram for Canister.
3. Scanner
1. Find and connect the sensor power line (Battery voltage), Ground line
(grounded by ECU) in referencing the wiring diagram.
2. Look at how the voltage is in connecting the Oscilloscope.
3. It must be measured with stepping on the accelerator pedal in other systems
except for BOSCH system because canister valve is opened with small duty in
idle state in BOSCH system But closed in the others.
< NOTICE1 >
It prefers not to use Multimeter because it is difficult to measure the canister
solenoid valve operating state with Multimeter in case of Duty control
(continuous ON/OFF type).
< NOTICE2>
In case of connecting the Auto-Scanner, Let’s reference the results because
Auto-scanner diagnoses some troubles automatically.
CANISTER PURGE VALVE-2
Comparing Method: After measuring the signal, compare the measured signal with
Normal signal.
(1) Compare the opening value ( Duty when the voltage is ‘0’) with the frequency
from normally measured signal.
(2) It would like to check the Canister operating state with connecting the Scanner.
< Checking items >
(1) Is the Frequency right?
(2) Check whether the canister valve is not opening even though operating or
opening even though not operating.
(3) Is there sensor operating voltage line / Ground line broken?
CANISTER PURGE VALVE-3
CANISTER PURGE VALVE-4
WAVE ANALYSIS
Canister solenoid valve characteristic is as followings:
1. Regular voltage / Ampere: 13.5V / 0.5 A
2. Internal resistance : 15 - 30 Ω
3. Operating voltage : 9 - 16 V
4. Operating frequency / Impulse : 10 - 20 Hz / 6 msec
5. Leakage : 0.002 m³/h
6. Fuel vapor gas flow characteristic :
CANISTER PURGE VALVE-5
WAVEFORM
CANISTER PURGE VALVE-6
< Reference >
Above example show flow rate of fuel vapor gas by intake manifold vacuum
with fully opening of solenoid valve which is controlled by duty cycle. Most
of vehicle have same trend but floe rate is different(The bigger and bigger
displacement, flow rate is big, ON/OFF type is only controlled from 20 to 40%)
CANISTER PURGE VALVE-7
FIELD EXAMPLE
< Example 1 >
Vehicle : New sephia / Avella 1.5L SOHC/DOHC, Odometer : 12,000Km
Problem
description : RPM is
unstable in idle after
start and it smell fuel
from exhaust gas.
Cause : The leakage
of purge solenoid
valve with warmed up
engine
Signal measurement : The power of purge solenoid
valve is off but it is abnormally opened.
CANISTER PURGE VALVE-8
Explanation : It is so difficult to check problem because purge valve is
opened with heated engine and it is normally operated with engine cool
down.
Enlargement of application : We can guess overflow of fuel supply by
engine vibration and fuel smell. Find conditions that occurring overflow
of fuel supply.
OXYGEN SENSOR HEATER-1
CHECK METHOD
1. Oscilloscope (It prefers not to use Multimeter available)
2. Wiring Diagram for Canister.
3. Scanner
1. Find and connect the sensor power line (Battery line), Ground line (grounded
by ECU) in referencing the wiring diagram.
2. Look at how the voltage is in connecting the Oscilloscope.
3. There is the other case of outside ground not grounded by ECU. : Reference the
wiring diagram.
< Reference>
It prefers not to use Multimeter because it is difficult to measure the Heater
operating state with Multimeter in case of Duty control (continuous ON/OFF
type).
OXYGEN SENSOR HEATER-2
OXYGEN SENSOR HEATER-3
WAVE ANALYSIS
Oxygen sensor heater power
OXYGEN SENSOR HEATER-4
Oxygen sensor tip temperature effect (Zirconium)
OXYGEN SENSOR HEATER-5
FIELD EXAMPLE
< Example 1 > The O2 sensor crack by dew point
Vehicle : B maker O2 sensor equipped vehicle
Problem description : O2 sensor crack is often occurred in fall and spring.
Signal measurement : O2 sensor signal is not measured.
OXYGEN SENSOR HEATER-6
Explanation : The vapor inside exhaust pipe is produced lots with ambient
temperature 10℃. This vapor wrap around O2 sensor and it result in
crack of tip. It is due to too fast heating for O2 sensor.
Enlargement of application : The O2 sensor should be heated after
avoiding dew point temperature. And stop O2 heater control with
temperature higher than 700℃so that O2 sensor tip should not be
heated too much. Therefore when exchanging non-heated type with
heated type O2 sensor, notice to customer that dew point problem may
be occurred.