OBD II UPDATE TRAINING
COURSE
OBD II Module Outline
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OBD II Foundation
OBD II History
OBD II Terminology
OBD I vs OBD II
OBD II MIL
Operation
• DTCs (A & B types
• OBD II Numbering
• Rationality /
Normality
• One/Two Trip DTCs
• Freeze Frame
• I/M Readiness
Monitors
SESSION 1
OBD I FOUNDATION
• Onboard Diagnostics Generation 2
– Not a stand alone system
– OBD II is built on top of OBD I
THE OBD I FOUNDATION
• OBD I mandated a “Check
Engine Light”
• Included diagnostic trouble
codes (DTCs)
THE OBD I FOUNDATION
• OBD I Mandated in 1988
• Objectives
– Improve emission compliance by
notifying the driver that there was a
malfunction
– Assist in identifying malfunctioning
circuits in the computer control system
OBD I MIL Operation
• Check Engine Light Operation
– Illuminated when circuit was abnormal
• Open, Shorted, Grounded
– Illuminated intermittently when circuit
operated abnormally intermittently
– Didn’t always illuminate when a problem
was detected!
– WAS INCONSISTENT!!!
Serial Data
• Live Computer Data
– Supplied by the vehicle’s computer
– Read via a Scan Tool
– Interpreted Data
– GM, Chrysler, then Ford
– Now mandated by OBD II
Diagnosing Today’s Vehicles
• Technician must have a strong
foundation in system operation &
theory!!!
• Technician must have ability to fully
utilize today’s tools
– Scan Tool, DSO, 5-gas analyzer, etc.
• Technician must know how theory &
tools are best applied together
OBD I
• On Board Diagnostics with a
Check Engine Light
• Mandated by CARB
• Gave birth to OBD II
OBD II Update Training Course
Session II
OBD II Foundation
Session 1
The OBD I Foundation
• OBD I - On Board Diagnostics
with a Check Engine Light
–MIL Operation Inconsistent
–DTC Viewing Method Inconsistent
–DTC Criteria Inconsistent
–DTC Numbering Inconsistent
The OBD II System
• The Second Generation was
designed to fix the inadequacies of
the First Generation
• One of the biggest problems was
the system must be monitored
under load!
OBD I Mode Monitoring
• Degraded emission systems did not set
Check Engine Light
• EVAP, CAT, & AIR were not monitored
• O2S Performance not monitored
• CAT killing misfires not monitored
• Shifted air fuel ratios not monitored
• NOx emissions not monitored (still?)
OBD II Strategies
• Implementation slated for 1996
models
• Phase in to begin 1994-1996
• OEMs allowed to EEPROM flash
to lock-out problems affecting CSI
– Check with manufacturer regarding
current configuration
Setting the Standards
• C.A.R.B - 1994 - 1998
• E.P.A. 1998 - On
• S.A.E.
–Requirements for common
systems
–Programming changes
OBD II Requirements
• Must be installed on all vehicles
• Must be able to determine
operating condition of the vehicle’s
emission control system / strategy
• Diagnostics & Functions must be
standardized
OBD II Requirements
• PCM must store DTCs for detected
faults
• DTC’s must stay in memory until
cleared following repair or until 40
consecutive warm-up cycles
– 80 consecutive warm-up cycles if misfire
and/or fuel control related
OBD II Requirements
• The system must test emission control
systems, record the results, and display
those results
• A MIL is mandatory
– must illuminate when a fault is detected (and
confirmed?)
– must remain illuminated until the fault is
corrected (3 tests)
OBD II Requirements
• Generic Scan Tool (GST)
• SAE J 1850 and/or ISO 9141 communication
protocol
• Must monitor ALL OBD II information
• Monitoring & DTC clearing procedures must
meet CARB & EPA standards
• Must display Parameter ID (PIDs)
• Freeze Frame Data
• PCM Parameters & Test Results
OBD II Requirements
• Monitor Test Results
• Comprehensive Component
Monitoring
–Input Normality & Rationality
–Outputs for performance or at
least electrically
The Scan Tool
(2 Tools In One?)
• OBD II Generic Scan Tool (GST)
• Manufacturer Specific Scan Tool
• Hybrid
– OBD II Generic with Manufacturer
Specific Capabilities
OBD II Commonalties
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Standardization Facilitated by SAE
SAE compromised of Reps from OEMs
OBD II guidelines established by SAE
OEMs interpreted guidelines differently
OBD II is the SAME, but DIFFERENT!
Emission Related Monitoring
• Unlike OBD I, OBD II not only
monitors an actuator was
commanded on, but tests the
system to make sure it actually
worked!!!
OBD II Monitors
• Designed to detect failures that would cause
emissions to increase by 50% or would
shorten the life of the catalytic converter
• The number of monitors are increasing
• Monitors require more computing resources
and additional sensors
• Monitors are run under specific conditions
OBD II Program Management
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Program Manager
Task Manager
Diagnostic Executive
OBD II Program Management
– Artificial Intelligence
– Rationality
OBD II Standardization
• Common Diagnostic Connector
– Data Link Connector (DLC)
– 16 pins -- 7 for SAE/OBD II & 9 for
OEM
– 1 pin is B+ to power Scan Tool
– DLC to be located on drivers side near
steering column or have a location label
MIL Regulations
• MIL will illuminate when an
increase in emissions = to 1.5 X
the FTP is inferred
• Or when the PCM/Network itself
malfunctions
• The MIL shall not be used for any
other purpose!!!
MIL Operation
• MIL On
– a fault has been detected (and
confirmed?)
• MIL Off
– No fault has been detected
– Test have not been run
• MIL Flashing
– Catalyst damaging misfire or air fuel
problem detected
Diagnostic Trouble Codes
• Common numbering system for all
DTCs
– Alpha Numeric
– 5 digit
• DTCs must be similar in meaning
• DTC designation must be common
• SAE standard J2012
DTC Numbering
• 1st Digit
– Alpha Character
– “P” - Powertrain
– “C” - Chassis
– “B” - Body
– “U” - Uart / multiplexing / networking
DTC Numbering
• 2nd Digit or thousandth position
• Either “1” or “0”
• “0” Codes are SAE / OBD II
Controlled
• “1” Codes are Manufacturer
Specific
DTC Numbering
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3rd Digit or hundredth position
System Fault
“100” - Fuel & Air Metering
“200” - Fuel & Air Metering (injector &
fuel pump)
• “300” - Misfire or Ignition System
• “400” - Emission Control
DTC Numbering
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3rd Digit or hundredth position
System Fault
“500” - Vehicle Speed and/or Idle Control
“600” - Computer Output Circuits
“700” - Transmission
“800” - Transmission
DTC Numbering
• 4th & 5th Digits - tens & ones
• Designate Specific Fault
• Example
–P0301 = Engine Cylinder # 1
Misfire Detected
Diagnostic Trouble Codes
OBD I vs. OBD II
1. OBD II requires “code enabling criteria”
be met (maybe twice) before a code is
stored. OBD I only needed abnormality
2. OBD II for emissions ONLY! OBD I is
not. Most OEMs recommend fixing OBD I
first - before checking / repairing OBD II
Diagnostic Trouble Codes
OBD I vs. OBD II
• OBD I diagnostic procedure was to…
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Pull Codes
Record Codes
Erase Codes
Operate Vehicle
Pull Codes
• Erasing OBD II Codes will also erase
Freeze Frame Data
Diagnostic Trouble Codes
OBD I vs. OBD II
• OBD II has no “soft codes”
• OBD II diagnostic procedure
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Pull Code
Record Freeze Frame Data
Repair Root Cause
Operate vehicle at Freeze Frame parameters
Meet code enable criteria
Run monitor
MULTIPLEXING
• Vehicles use multiple onboard
computers
• Faults in other computers can disable
monitors due to multiplexing
• Example
– Wheel Speed Sensors used to verify
rough road to prevent false misfire codes
Code Enable Criteria
• Definition
– “Once the conditions are met to test for the
DTC are met, then the monitor will run the test”
• P0134 - HO2S - 11 Remains At Center (B1
S1) Code Conditions:
– Engine runtime over 2 minutes, ECT sensor
input more than 176 degrees F, then the test
started and the PCM detected that the front
HO2S-11 signal was 0.5v (fixed at mid-range
for 1 minute)
ONE TRIP DTCs
• MIL will illuminate after one DTC
enable criteria has been met and failed!
• Most common One Trip failures are…
– Misfire & Fuel Control Monitors
– CCM will depending on manufacturer
• TPS, MAP, MAF, ECT, CKP, etc.
TWO/THREE TRIP DTCs
• MIL will illuminate when DTC
enable criteria are met and
failed in 2 consecutive trips
• Compromise for CSI
• DTC confirmation
TWO/THREE TRIP DTCs
• When 1st trip fails
–Code is “pending” or “maturing”
–Freeze Frame data is captured,
but not displayed
–MIL is off
TWO/THREE TRIP DTCs
• If & When 2nd trip fails…
– MIL is illuminated
– Code “matures” & DTC is set
– Freeze Frame Data can be viewed
• Same with 3 trip failures…
– Except add 1 trip
PENDING DTCs
• If 2nd trip passes (doesn’t fail)…
– Pending Code stays pending for 40
good trips or 80 good trips for
misfire / air fuel
– Freeze Frame Data is displayed
– MIL stays off
MIL Strategies & DTCs
First Trip Failure
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MIL Command:
MIL “bad trip” counter:
MIL “good trips”:
DTC Command:
DTC “bad trips”:
DTC “good trips”
Pending DTC:
Pending “good trips”:
Freeze Frame Data:
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Off
One “bad trip”
N/A
Off
One “bad trip”
N/A
Set
N/A
Set, but not displayed
MIL Strategy
Exercise
MIL Strategies & DTCs
2nd Consecutive Trip Failure
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MIL Command:
MIL “bad trip” counter:
MIL “good trips”:
DTC Command:
DTC “bad trips”:
DTC “good trips”:
Pending DTC:
Pending “good trips”:
Freeze Frame Data:
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On
Reset to zero
N/A
Set & Displayed
Reset to zero
N/A
Set or cleared
N/A
Displayed
MIL Strategies & DTCs
2nd Consecutive Trip Pass
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MIL Command:
MIL “bad trip” counter:
MIL “good trips”:
DTC Command:
DTC “bad trips”:
DTC “good trips”:
Pending DTC:
Pending “good trips”:
Freeze Frame Data:
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Off
Reset to zero
N/A
Off
Reset to zero
N/A
Set or cleared
One “good trip”
Displayed or not
MIL Strategies & DTCs
Fault Repaired / DTC Not Cleared
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MIL Command:
MIL “bad trip” counter:
MIL “good trips”:
DTC Command:
DTC “bad trips”:
DTC “good trips”:
Pending DTC:
Pending “good trips”:
Freeze Frame Data:
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On
Reset to zero
N/A
Set & displayed
Reset to zero
N/A
Set or cleared
N/A
Displayed
DTC Priority Designation
• Type “A” DTCs
– Usually “One Trip” codes
– CAT Damaging or 1.5 X FTP
• Type “B” DTCs
– Usually “2 or 3 Trip” codes
– Serious failure
• Type “C” & “D” DTCs
– Not emission related / won’t illuminate MIL
DTC Clearing
• Automatic Code Clearing
– After 40 warm-up cycles with no re-occurrence
– Or
– After 80 warm-up cycles with no re-occurrence
for misfire or fuel control codes
– Freeze Frame Data gets erased as well
• Manual Code Clearing
– Through Scan Tool or battery disconnect
Common Terminology &
Vocabulary
• Vernacular Standardization / “New Speak”
• Standardization of Terms
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ALDL - DLC
EGO - O2S or HO2S
MAT - IAT
Integrator/Block Learn - STFT/LTFT
ESS - CKP
FREEZE FRAME DATA
• The exact second of data that set the DTC
• Mandated Data
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Calculated Engine Load
Engine Coolant Temperature
Loop Status (open or closed)
STFT / LTFT
Vehicle Speed (mph)
Engine Speed (rpm)
DTC set
FREEZE FRAME DATA
• Freeze Frame Data
– 1st failed trip of 1st DTC
– Not overridden by subsequent DTCs
– UNLESS!
– Subsequent DTCs are of a higher priority
– “A” Type Codes (misfires & fuel control)
or a higher priority than “B” Type Codes.
DTC / Freeze Frame
Exercise
OBD II Diagnostics
• Scan Tool Enhancements
– Expanded Information - manufacturer specific
– Expanded Description
• Troubleshooter - Pathfinder
– Identification of Responding PCM
• VIN - CAL ID
– Vehicle Preparation
• Warm-ups, Trips, Drive-cycles
OBD II Diagnostics
• Scan Tool Enhancements (cont’d)
– Diagnostic Procedures
• Troubleshooter - Pathfinder
– Repair Verification
• Reset, relearn, adaptive strategies
– PID Description & Values
• sensor specifications
– Test Procedures
• Actuators
• Miscellaneous
OBD II Diagnostics
• Scan Tool Enhancements (cont’d)
– DTC Library
• code description & enable criteria
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O2S location & type
Sensor Simulator
EEPROM Flashing
Replacement PCM Programming
OBD II Update Training Course
Session II
OBD II Foundation
Session 1
The OBD I Foundation
• OBD I - On Board Diagnostics
with a Check Engine Light
–MIL Operation Inconsistent
–DTC Viewing Method Inconsistent
–DTC Criteria Inconsistent
–DTC Numbering Inconsistent
The OBD II System
• The Second Generation was
designed to fix the inadequacies of
the First Generation
• One of the biggest problems was
the system must be monitored
under load!
OBD I Mode Monitoring
• Degraded emission systems did not set
Check Engine Light
• EVAP, CAT, & AIR were not monitored
• O2S Performance not monitored
• CAT killing misfires not monitored
• Shifted air fuel ratios not monitored
• NOx emissions not monitored (still?)
OBD II Strategies
• Implementation slated for 1996
models
• Phase in to begin 1994-1996
• OEMs allowed to EEPROM flash
to lock-out problems affecting CSI
– Check with manufacturer regarding
current configuration
Setting the Standards
• C.A.R.B - 1994 - 1998
• E.P.A. 1998 - On
• S.A.E.
–Requirements for common
systems
–Programming changes
OBD II Requirements
• Must be installed on all vehicles
• Must be able to determine
operating condition of the vehicle’s
emission control system / strategy
• Diagnostics & Functions must be
standardized
OBD II Requirements
• PCM must store DTCs for detected
faults
• DTC’s must stay in memory until
cleared following repair or until 40
consecutive warm-up cycles
– 80 consecutive warm-up cycles if misfire
and/or fuel control related
OBD II Requirements
• The system must test emission control
systems, record the results, and display
those results
• A MIL is mandatory
– must illuminate when a fault is detected (and
confirmed?)
– must remain illuminated until the fault is
corrected (3 tests)
OBD II Requirements
• Generic Scan Tool (GST)
• SAE J 1850 and/or ISO 9141 communication
protocol
• Must monitor ALL OBD II information
• Monitoring & DTC clearing procedures must
meet CARB & EPA standards
• Must display Parameter ID (PIDs)
• Freeze Frame Data
• PCM Parameters & Test Results
OBD II Requirements
• Monitor Test Results
• Comprehensive Component
Monitoring
–Input Normality & Rationality
–Outputs for performance or at
least electrically
The Scan Tool
(2 Tools In One?)
• OBD II Generic Scan Tool (GST)
• Manufacturer Specific Scan Tool
• Hybrid
– OBD II Generic with Manufacturer
Specific Capabilities
OBD II Commonalties
•
•
•
•
•
Standardization Facilitated by SAE
SAE compromised of Reps from OEMs
OBD II guidelines established by SAE
OEMs interpreted guidelines differently
OBD II is the SAME, but DIFFERENT!
Emission Related Monitoring
• Unlike OBD I, OBD II not only
monitors an actuator was
commanded on, but tests the
system to make sure it actually
worked!!!
OBD II Monitors
• Designed to detect failures that would cause
emissions to increase by 50% or would
shorten the life of the catalytic converter
• The number of monitors are increasing
• Monitors require more computing resources
and additional sensors
• Monitors are run under specific conditions
OBD II TRAINING MODULE
OBD II MAIN MONITORS
READINESS FLAGS
• Definition
– Tells you via Scan Tool if monitor
has been completed
• Done, Ready, Readiness Test Complete
– Does not tell you the outcome!!!
• If pass once or twice - no code
• If fail once or twice - DTC
SYMPTOM WITHOUT CODES
• Run 2 or 3 drive cycles…
• Check for DTCs & Pending DTCs
• If no OBD II problems detected then…
– Check mechanical, electrical, ignition,
emissions, fuel, and any other non
computer monitored system
OBD II “TRIPS”
• Definition…
– A set of operating conditions to be met in order
to run a monitor so that the test is valid and
drive-ability is not sacrificed.
• Purpose / Objectives
– To test a component or system
– To verify complaint
– To verify repair effectiveness
OBD II “DRIVE CYCLES”
• Definition…
–A specific set of operating
conditions that enable ALL
“trips” to complete and ALL
monitors to run
OBD II “WARM-UP CYCLES”
• Definition…
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ECT must begin below and rise above 160° F
ECT must rise at least 40° F
No further faults occur
Sometimes includes CTS and BTS (IAT) be
within 10° F of each other
• Purpose / Objectives
– Erase DTCs & Freeze Frame
– Enable criteria for some DTCs & Trips
FUEL LEVEL INPUT
• Fuel Level should be between…
– 15% & 85%
– 25% & 75%
• If not…
– Some Monitors will not run!
• For Example…
– EGR, EVAP Leak, EVAP Flow, & Fuel
System need fuel level above 15%
OBD II Monitors
• Comprehensive
Component
Monitor
• Catalyst
Efficiency
Monitor
• Misfire Monitor
• EGR Monitor
• EVAP Monitors
• Fuel System
Monitor
• Oxygen Sensor
Monitors
• Secondary Air
Monitor
COMPREHENSIVE
COMPONENT MONITOR
• Definition…
– A continuous look at a lot of something
• Sensors - VSS, CKP, KS, TPS, CTS, CMP
• Outputs - Any and all outputs that could
affect emissions
• Checks for “Normality” constantly
• Checks for “Rationality” when enable
criteria is reached
COMPREHENSIVE
COMPONENT MONITOR
• All “Rationality” checks should be
performed in the course of a
“Drive Cycle”
• DTCs could be 1 or 2 trip codes
CATALYST EFFICIENCY
MONITOR
• Infers Catalyst efficiency by
comparing pre & post O2S operation
• A working oxidation consumes O2 in
order to oxidize HC & CO into Water
& CO2
• A working catalyst uses Cerium that
stores and releases O2 to enhance
efficiency
CATALYST EFFICIENCY
MONITOR
• Upstream O2S should oscillate
• Downstream activity should not be within
70% of Upstream
• Generic Enable Criteria is as follows:
– ECT >170°, Closed Loop for at least 3 minutes,
RPM between 1,200 & 2,500, Vehicle Speed at
least 20 mph for 3 minutes, MAP between 11” 15” hg, and fuel level over 15%
CATALYST EFFICIENCY
MONITOR
• DTC - P0420
– Set when monitor is run and fails
– Might be due to defective catalyst
– Could be caused by O2S performance, ECT too
low, exhaust leak, etc…
• This monitor doesn’t check the reduction
portion of the catalyst
• The upstream & downstream O2Ss are NOT
the same!!!
MISFIRE MONITOR
• Misfires result in HC failures
• Misfires damage catalysts
• Two types of misfires
– “A” & “B” misfires
– “A” identifying SEVERE misfires
– Type “A” misfires might result in MIL
flashing
MISFIRE DETECTION
• Relies on CKP Sensor
• Usually Variable Reluctor
• PCM looks for asymmetrical signal
– either frequency or amplitude
• Some vehicles use Hall-Effect
• Some vehicles use a totally separate sensor
MULTIPLE MISFIRES
• DTC - P0300
– Random / Multiple Misfire Detected
• Usually the cylinder that is misfiring is
identified by the code
• Depending on the % of time a cylinder is
misfiring it will be designated “A” or “B”
• Remember - A type “A” misfire will overwrite previous Freeze Frame Data!
MISFIRE MONITORS
“ROUGH ROAD”
• Vibration due to rough roads could result in
false P0300 DTCs
• Some manufacturers refer to wheel speed
sensors to verify rough road conditions
• If rough road is verified - misfire monitor is
suspended.
• Faulty wheel speed sensor circuits can
prevent misfire monitor
• Check OBD I codes first!!!
MISFIRE MONITOR
DIAGNOSIS
• OBD II Misfire Monitor can be more
sensitive than an ignition oscilloscope!
• Verify misfire with DSO connected to…
– CKP or Misfire Sensor and map signal when
MIL illuminates
– Upstream O2S and map signal within 10% of
Freeze Frame Data
• O2S won’t tell you which cylinder - just that a
misfire is occurring.
EGR MONITOR
• EPA Requirement for monitoring EGR
system…
– The diagnostic system shall monitor the
EGR system on vehicles so equipped for
low & high flow rate malfunctions.
• Monitoring Alternatives
– MAP, O2S, Temperature
EGR MONITOR
MAP
• Manifold Pressure is monitored during EGR
system operation to determine flow rate
– Usually on deceleration
• Monitoring Performed by Pressure
Differential Sensor
– Same as MAP, but with different name
• Lower than expected pressure infers low
flow rate. Higher than expected pressure
infers excessively high flow rate.
EGR MONITOR
OXYGEN SENSOR TEST
• Energizing EGR system removes O2
from combustion chamber
• De-energizing EGR system increases
O2 in combustion chamber
• PCM monitors how long it takes fuel
trim to put O2 back on track to
measure flow rate
EGR MONITOR
TEMPERATURE SENSING
• Sensor installed in EGR
passage
• PCM determines EGR flow rate
by monitoring temperature
EGR MONITOR
ENABLE CRITERIA
• Varies from manufacturer to manufacturer
• Typical enable criteria as follows:
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Closed Loop
Steady cruise (40-55 mph) for three minutes
Deceleration from steady cruise (no braking)
No other DTCs associated with EGR or
monitoring system
• Usually 2 trip DTC
EVAP MONITOR
• EPA Requirements for monitoring EVAP
system…
– The diagnostic system shall verify air flow
from the complete system. In addition, the
diagnostic system shall also monitor the
evaporative system for the loss of HC vapor
into the atmosphere by performing a pressure or
vacuum check of the complete evaporative
system. Manufacturers may temporarily
disable the evaporative purge system to perform
a check.
EVAP MONITOR
• Malfunction Criteria
– No purge is occurring
– A leak = or > 0.040” (0.020” in the future)
• MIL Illumination and DTC storage
– Usually a 2 trip code
• Remember!
– Fuel tank must be between 15% & 85%
(25% & 75%)
EVAP MONITOR
• Purpose of EVAP system
– To store HCs that would have otherwise
evaporated into the atmosphere and purge
them into the induction system for
burning.
– A leak = 0.020” will allow 1.35 grams of
HCs into the atmosphere for every mile
traveled!
EVAP MONITOR
• All EVAP Monitors require a warm-up
cycle! EVAP tested once per drive cycle!
• OBD II uses 1 or 2 EVAP system vent
solenoids (isolate system)
• Differential Pressure Sensors (EGR
Monitor?)
– reads pressure in inches of water. 1 inch = .25”
of mercury (HG)
EVAP MONITOR
• 2 Methods of testing the
system for integrity
–Vacuum testing
–Pressure Testing
EVAP MONITOR
• Vacuum Testing
–Seal the system
–Pull a vacuum
–Monitor the Differential
Pressure Sensor over time
EVAP MONITOR
• Pressure Testing
– Seal the system
– Pump up a pressure
– Monitor Differential Pressure Sensor over
time
• More accurate than Vacuum Testing
because vacuum can sometimes
temporarily seal a small leak.
EVAP MONITOR
• Code Enable Criteria
– Varies manufacturer to manufacturer
– One manufacturer’s criteria is as follows:
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•
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•
Fuel tank level is between 15% & 85%
Engine off (soak) time 6 hours minimum
Time since start-up between 330 & 1800 seconds
IAT between 40° & 100° F
BARO (<8,000 ft. altitude), minimum 22.5” HG
EVAP MONITOR
• Code Enable Criteria (cont’d)
– Engine Load between 20% & 70%
– VSS between 40 & 75 mph
– Purge duty cycle between 75% &
100%
– Fuel tank pressure between 1.7” &
2.5” H2O
EVAP MONITOR
• Usual DTC’s
– P0450 - Evaporative Emission Control
System Vent Valve/Solenoid Circuit
Malfunction
– P0455 - Evaporative Emission Control
System Leak Detected (Gross Leak)
– P0442 - Evaporative Emission Control
System Leak Detected (Small Leak)
EVAP MONITOR
FAILURE DIAGNOSIS
• Scan Tool EVAP Test
– Manufacturers Scan Tool ability
– Scan Tool can operate vent solenoids to seal the
system
– Scan Tool can cycle purge solenoid to pull a
vacuum on system and then seal it off
– Scan Tool will monitor Differential Pressure
Sensor to determine if a leak exists and if it is
large or small
EVAP MONITOR
FAILURE DIAGNOSTICS
• Smoke Machine EVAP Testing
– Use Scan Tool and seal the system
– Open EVAP system and introduce
smoke or use schrader adapter (green
cap)
– CAUTION - watch the pressure!!!
– Watch for escaping smoke
EVAP MONITOR
FAILURE DIAGNOSIS
• Dedicated Tester
– Pressure pump with gauge that reads
inches of water (not mercury)
– Doesn’t help in isolating the leak just verifies there is a leak
EVAP MONITOR
FAILURE DIAGNOSIS
• Gas Analyzer Testing
– Isolate / Seal the system as necessary
– Pressurize the system
– Use gas analyzer as you would a
halogen leak detector for AC work
• Gas Cap Testers
FUEL SYSTEM MONITOR
• EPA requirements for monitoring
Fuel System…
– The diagnostic system shall monitor
the fuel delivery system for its
ability to provide compliance with
emissions standards
FUEL SYSTEM MONITOR
• Continuously monitored whenever
ignition is on!
• Usually type “A” DTCs (one trip)
• Relies on fuel trim data directly
and O2S data indirectly
FUEL SYSTEM MONITOR
• OBD I Terms
– Carburetor Dwell
– Duty Cycle
– Voltage
– Integrator / Block Learn
FUEL SYSTEM MONITOR
• Fuel Trim
– Short Term
– Long Term
• Values
– + % #s mean fuel is being added over base
calculations
– - % #x mean fuel is being subtracted over base
calculations
– usually + or - 10% is acceptable
OXYGEN SENSOR MONITOR
• EPA Requirements for monitoring the
Oxygen Sensor…
– The diagnostic system shall monitor the output
voltage, response rate, and any other parameter
which can effect emissions, of all primary (fuel
control) oxygen (lambda) sensors for
malfunction. It shall also monitor all secondary
oxygen sensors (fuel trim control or use as a
monitoring device) for proper output voltage
and/or response rate
OXYGEN SENSOR MONITOR
• EPA Requirements for monitoring the
Oxygen Sensor (cont’d)…
– Response rate is the time required for the
oxygen sensor to switch from lean to rich once
it is exposed to a richer than stoichiometric
exhaust gas or vice versa (measuring oxygen
sensor switching frequency may not be an
adequate indicator of oxygen sensor response
rate, particularly at low speeds)
OXYGEN SENSOR MONITOR
• EPA Requirements for monitoring the
Oxygen Sensor (cont’d)…
– For vehicles equipped with heated oxygen
sensors, the heater circuit shall be monitored for
proper current and voltage drop (note: a
continuity check of oxygen sensors is not
required)
O2S MONITORING
• 3 TESTS ARE PERFORMED…
– First test is for calibration.
• Is the sensor operating between allowable
tolerances?
– Second test is switching time.
• How long does it take to go from rich to lean or vice
versa?
– Third test is frequency
• O2S activity under normal (?) conditions
SECONDARY AIR
MONITORING
• EPA Requirements for monitoring
Secondary Air operation
– Any vehicle equipped with any form of
secondary air delivery system shall have
the diagnostic system monitor the proper
functioning of the secondary air delivery
system and any air switching valve.
SECONDARY AIR
MONITORING
• Two Common Tests…
– 1. Widen injector pulse width for a
artificially rich condition & monitor O2S.
Pump Secondary Air upstream and
monitor O2S
– 2. Monitor STFT / LTFT and pump
Secondary Air upstream
OBD II UPDATE TRAINING
Round-Up
MALFUNCTION INDICATOR LIGHT
(MIL)
• MIL Status
– Off
• PCM has not detected any faults in an emission
related component or system, or MIL is inop
– On Steady
• indicates a fault in an emissions related component
or system that could affect emission levels
– Flashing
• misfire or fuel control system fault that could
damage catalytic converter
MALFUNCTION INDICATOR LIGHT
(MIL)
• Turning Off the MIL
– Codes are cleared through scan tool
– Power to PCM is removed
• disconnect battery
• remove fuse(s)
• doesn’t always work
– 3 consecutive trips are completed without
further faults detected
SIMILAR CONDITIONS
FUEL & MISFIRE
• Engine RPM within 375 of stored
Freeze Frame Data
• Engine Load within + or - 10% of
stored Freeze Frame Data
• Engine Coolant Temperature similar to
stored Freeze Frame Data
DIAGNOSTIC TROUBLE CODES
(DTCs)
• 5 Digit - Alpha-numeric DTCs
– First Digit (reading from left to right)
• Designates either powertrain (P), Body (B),
Chassis (C), or Network (U)
– Second Digit
• Designates DTC as SAE Generic (0) or
Manufacturer Specific (1)
DIAGNOSTIC TROUBLE CODES
(DTCs)
– Third Digit
• Designates Faulted System
–
–
–
–
–
–
–
1-Air Metering & Fuel System
2-Fuel System (fuel injector only)
3-Ignition System or Misfire
4-Emission Control System
5-Idle Speed / Vehicle Speed
6-Computer Outputs
7&8-Transmission & Transaxles
– Fourth & Fifth Digits
• Designates Specific Fault
DIAGNOSTIC TROUBLE CODES
(DTCs)
• DTC Types
– “A” - One trip codes
– “B” - All Other
• DTC Erasure
– Scan Tool
– Removing Power from PCM (sometimes)
– Automatic after 40 warm-up cycles with no
further faults detected or 80 warm-up cycles for
misfire & fuel system
FREEZE FRAME DATA
• Definition - a single frame of data that displays at
a minimum the following data:
–
–
–
–
–
–
–
–
Calculated Engine Load (%)
Engine Coolant Temperature (ECT)
Fuel System Status (OL or CL)
Short Term Fuel Trim (STFT)
Long Term Fuel Trim (LTFT)
Miles Per Hour (MPH)
Engine Speed (RPM)
DTC Set
FREEZE FRAME DATA
• Captured when either pending or mature DTC is
set & MIL is illuminated
• Only 1 is stored
– For the first DTC only
• A misfire of fuel control DTC of a higher priority
can overwrite a lower priority Freeze Frame
• Only the Freeze Frame will be overwritten - not
the DTC!!!
FREEZE FRAME DATA
• Uses…
– Diagnostics - to analyze the conditions the
vehicle was being operated when the fault
appeared
– Repair Verification - Fuel System & Misfire
MILs can only be turned off after 3 trips under
similar conditions
FUEL TRIM
• The ability of the computer to deviate from
the look-up table
• A low O2 voltage/lean exhaust will result in
the Fuel Trim adding fuel / + % #s
• A high O2 voltage/rich exhaust will result
in the Fuel Trim subtracting fuel / - % #s
EVAP MONITOR
• The object of this monitor is to verify
canister is being purged and that the
systems is not leaking fuel vapors into the
atmosphere (0.040 / 0.020 size leak)
• Pressure is done via a Differential Pressure
Sensor measuring vacuum or pressure
• Purge is done by measuring O2 and/or Fuel
Trim
• 2 trip DTC/MIL
O2S MONITOR
• Tests all Oxygen Sensors
• O2 Sensors must be calibrated
– minimum voltage
– maximum voltage
• O2 Sensors must react fast
– activity
– rate of change
• 2 trip DTC/MIL
Oxygen Sensor
• Location Designation
– The lower the number, the closer the
sensor to the front of the engine or front
of the bank
– Bank 1 is where cylinder #1 is
– Bank 2 is the other bank
– The highest number usually designates
the post-O2S
COMPREHENSIVE COMPONENT
MONITOR
(CCM)
• Continuous Monitor of emission control
related items not specifically monitored by
the task manager.
• Constantly monitors for opens, shorts, and
grounds,
• Can monitor rationality if enable criteria is
met
• DTC’s can be 1 or 2 trip
Continuous & Non-Continuous
Monitors
• Continuous
– Misfire
– Fuel System
– Comprehensive
Component
Monitor
• Non-Continuous
– Catalyst
– EGR
– EVAP
– O2S
– O2S Heater
– Catalyst Heater
– AIR
CATALYST MONITOR
• Objective is to determine if catalytic converter is
operative
• Compares the frequency & amplitude of Pre &
Post O2Ss (voltage level?)
• If Post O2S activity is similar to of Pre O2S
– Cat must not be working
– O2S might be bad
– Conditions needed to operated cat might not be being
created
• Monitor is run once per trip and DTC is a 2 tripper
MISFIRE MONITOR
• Objective is to detect misfires that could
elevate emission by 50% and/or damage
catalyst
• Main misfire sensor is engine speed
– CKP & CMP
• 2 types of misfires
– Catalyst damaging (severe) - flashing MIL
– Misfire that will result in emissions rising 50%
above FTP
• Enable criteria includes - MAP, RPM, ECT,
Start-to-run time, & VSS
DEFINITIONS
• OBD II - Gov’t regulations that mandate
faults that result in a 50% increase in
emissions be identified, the operator
warned, and diagnostics standardized.
• Warm-Up Cycle - Start-to-run where ECT
increases 40° F and the temperature rises
above 160° F
• Rationality - comparing sensor/actuator
values against others to determine their
calibration
GENERIC SCAN TOOLS
(GST)
• WILLs
–
–
–
–
–
Read PIDs
Read Readiness Status
DTC’s
Freeze Frame Data
Connect to any OBD II
vehicle
• WON’Ts
– Be as fast as vehicle
specific or Hybrid
– Diagnose vehicle for
you
– Fix vehicle for you
TRIPS
• Definition
– A sequence of events and a set of
conditions that must be met for a specific
monitor to run
• Uses
– To test a system to verify a complaint or
repair
– To turn on or turn off MIL
OBD II DIAGNOSTICS
• DTCs cannot be verified unless
code enable criteria has been met
• For OBD II to work correctly all
OBD I systems have to be OK
• No communication problems can
sometimes be diagnosed at the
DLC