OBD port ISUZU TROOPER 1998 Service Repair Manual

6E±1 ENGINE DRIVEABILITY AND EMISSIONS
ENGINE
ENGINE DRIVEABILITY AND EMISSIONS
CONTENTS
Specifications 6E±5. . . . . . . . . . . . . . . . . . . . . . . . .
Tightening Specifications 6E±5. . . . . . . . . . . . . . .
Vehicle Type Specifications 6E±5. . . . . . . . . . . . .
Diagrams and Schematics 6E±6. . . . . . . . . . . . . . . .
PCM Wiring Diagram (1 of 11) 6E±6. . . . . . . . . . .
PCM Wiring Diagram (2 of 11) For EC,
THAILAND, SOUTH EAST ASIA, LATIN
AMERICA, GULF, SAUDI, CHINA. 6E±7. . . . . .
PCM Wiring Diagram (3 of 11) For SOUTH
AFRICA and EXP. 6E±8. . . . . . . . . . . . . . . . . . . . .
PCM Wiring Diagram (4 of 11) 6E±9. . . . . . . . . . .
PCM Wiring Diagram (5 of 11) 6E±10. . . . . . . . . . .
PCM Wiring Diagram (6 of 11) For
AUSTRALIA, THAILAND, SOUTH EAST
ASIA, LATIN AMERICA, GULF, SAUDI,
LATIN AMERICA. 6E±11. . . . . . . . . . . . . . . . . . . . .
PCM Wiring Diagram (7 of 11) For EC. 6E±12. . .
PCM Wiring Diagram (8 of 11) For EXPORT
and SOUTH AFRICA. 6E±13. . . . . . . . . . . . . . . . .
PCM Wiring Diagram (9 of 11) Except EXP
and SOUTH AFRICA 6E±14. . . . . . . . . . . . . . . . . .
PCM Wiring Diagram (10 of 11) For
EXPORT and SOUTH AFRICA 6E±15. . . . . . . . .
PCM Wiring Diagram (11 of 11) 6E±16. . . . . . . . . .
PCM Pinouts 6E±17. . . . . . . . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 32-Way Red
Connector ± Row ªAº 6E±17. . . . . . . . . . . . . . . . . .
PCM Pinout Table, 32-Way Red
Connector ± Row ªBº 6E±19. . . . . . . . . . . . . . . . . .
PCM Pinout Table, 32-Way White
Connector ± Row ªCº (For EC) 6E±20. . . . . . . . . .
PCM Pinout Table, 32-Way White
Connector ± Row ªCº (For except EC) 6E±21. . .
PCM Pinout Table, 32-Way White
Connector ± Row ªDº
(For except EXPORT and SOUTH
AFRICA) 6E±22. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 32-Way White
Connector ± Row ªDº
(For EXPORT and SOUTH AFRICA) 6E±23. . . . .
PCM Pinout Table, 32-Way Blue
Connector ± Row ªEº
(For except EXPORT and SOUTH
AFRICA) 6E±24. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 32-Way Blue
Connector ± Row ªEº
(For EXPORT and SOUTH AFRICA) 6E±26. . . . .
PCM Pinout Table, 32-Way Blue
Connector ± Row ªFº 6E±27. . . . . . . . . . . . . . . . . .
Component Locators 6E±28. . . . . . . . . . . . . . . . . . . .
Engine Component Locator (This illustration
is based on RHD model.) 6E±28. . . . . . . . . . . . . . Engine Component Locator Table 6E±29. . . . . . . .
Engine Component Locator Table 6E±31. . . . . . . .
Undercarriage Component Locator 6E±32. . . . . .
Undercarriage Component Locator Table
(Automatic Transmission) 6E±32. . . . . . . . . . . . . .
Undercarriage Component Locator Table
(Manual Transmission) 6E±33. . . . . . . . . . . . . . . .
Fuse and Relay Panel (Underhood
Electrical Center) 6E±33. . . . . . . . . . . . . . . . . . . . .
Sensors and Miscellaneous Component
Locators 6E±34. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnosis 6E±37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Strategy-Based Diagnostics 6E±37. . . . . . . . . . . . .
Strategy-Based Diagnostics 6E±37. . . . . . . . . . . . .
DTC Stored 6E±37. . . . . . . . . . . . . . . . . . . . . . . . . . .
No DTC 6E±37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
No Matching Symptom 6E±37. . . . . . . . . . . . . . . . .
Intermittents 6E±37. . . . . . . . . . . . . . . . . . . . . . . . . .
No Trouble Found 6E±37. . . . . . . . . . . . . . . . . . . . .
Verifying Vehicle Repair 6E±37. . . . . . . . . . . . . . . .
General Service Information 6E±38. . . . . . . . . . . . . .
OBD Serviceablity Issues 6E±38. . . . . . . . . . . . . . .
Maintenance Schedule 6E±38. . . . . . . . . . . . . . . . .
Visual / Physical Engine Compartment
Inspection 6E±38. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Knowledge of Tools Required 6E±38. . . . . .
Serial Data Communications 6E±38. . . . . . . . . . . . . .
Class II Serial Data Communications 6E±38. . . . .
On-Board Diagnostic (OBD) 6E±39. . . . . . . . . . . . . .
On-Board Diagnostic Tests 6E±39. . . . . . . . . . . . .
Comprehensive Component Monitor
Diagnostic Operation 6E±39. . . . . . . . . . . . . . . . . .
Common OBD Terms 6E±40. . . . . . . . . . . . . . . . . .
The Diagnostic Executive 6E±40. . . . . . . . . . . . . . .
DTC Types 6E±41. . . . . . . . . . . . . . . . . . . . . . . . . . .
Verifying Vehicle Repair 6E±42. . . . . . . . . . . . . . . .
Reading Diagnostic Trouble Codes Using
A Tech 2 6E±42. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tech 2 Tech 2 6E±43. . . . . . . . . . . . . . . . . . . . . . . . .
Tech 2 Features 6E±43. . . . . . . . . . . . . . . . . . . . . . .
Getting Started 6E±44. . . . . . . . . . . . . . . . . . . . . . . .
Operating Procedure (For Example) 6E±44. . . . .
DTC Modes 6E±45. . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC Information Mode 6E±46. . . . . . . . . . . . . . . . .
Injector Balance Test 6E±46. . . . . . . . . . . . . . . . . . .
EGR Control Test 6E±47. . . . . . . . . . . . . . . . . . . . . .
Idle Air Control System Test 6E±48. . . . . . . . . . . . .

6E±2
ENGINE DRIVEABILITY AND EMISSIONS
Primary System-Based Diagnostic 6E±50. . . . . . . . .
Primary System-Based Diagnostic 6E±50. . . . . . .
Fuel Control Heated Oxygen Sensor 6E±50. . . . .
HO2S Heater 6E±50. . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Trim System Monitor Diagnostic
Operation 6E±50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Trim System Monitor Diagnostic
Operation 6E±50. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Trim Cell Diagnostic Weights 6E±50. . . . . . .
On-Board Diagnostic (OBD) System Check 6E±51.
A/C Clutch Control Circuit Diagnosis 6E±54. . . . . . .
Electronic Ignition System Diagnosis 6E±60. . . . . . .
Fuel Metering System Check 6E±60. . . . . . . . . . . . .
Idle Air Control (IAC) Valve 6E±60. . . . . . . . . . . . . . .
Fuel System Pressure Test 6E±60. . . . . . . . . . . . . . .
Fuel Injector Coil Test Procedure and Fuel
Injector Balance Test Procedure 6E±60. . . . . . . . . .
Knock Sensor Diagnosis 6E±65. . . . . . . . . . . . . . . . .
Powertrain Control Module (PCM) Diagnosis 6E±65
Multiple PCM Information Sensor DTCS Set 6E±65
Exhaust Gas Recirculation (EGR) Diagnosis
(For except EXPORT and
SOUTH AFRICA) 6E±68. . . . . . . . . . . . . . . . . . . . . . .
Engine Tech 2 Data Definitions and Ranges 6E±68
Typical Scan Data Values 6E±70. . . . . . . . . . . . . . . .
No Malfunction Indicator Lamp (MIL) 6E±74. . . . . . .
Malfunction Indicator Lamp (MIL) ªONº
Steady 6E±77. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Cranks But Will Not Run 6E±79. . . . . . . . . . .
Fuel System Electrical Test 6E±85. . . . . . . . . . . . . . .
Fuel System Diagnosis 6E±88. . . . . . . . . . . . . . . . . . .
Idle Air Control (IAC) System Check 6E±93. . . . . . .
Knock Sensor (KS) System Check
(Engine Knock, Poor Performance, or Poor
Economy) 6E±95. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust Gas Recirculation (EGR) System
Check 6E±97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manifold Absolute Pressure (MAP) Output
Check 6E±99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PCM Diagnostic Trouble Codes 6E±101. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0101
MAF System Performance 6E±104. . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0102
MAF Sensor Circuit Low Frequency 6E±107. . . . . .
Diagnostic Trouble Code (DTC) P0103
MAF Sensor Circuit High Frequency 6E±110. . . . . .
Diagnostic Trouble Code (DTC) P0107
MAP Sensor Circuit Low Voltage 6E±112. . . . . . . . . .
Diagnostic Trouble Code (DTC) P0108
MAP Sensor Circuit High Voltage 6E±115. . . . . . . . .
Diagnostic Trouble Code (DTC) P0112
IAT Sensor Circuit Low Voltage 6E±118. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0113
IAT Sensor Circuit High Voltage 6E±121. . . . . . . . . . Diagnostic Trouble Code (DTC) P0117
ECT Sensor Circuit Low Voltage 6E±124. . . . . . . . . .
Diagnostic Trouble Code (DTC) P0118
ECT Sensor Circuit High Voltage 6E±127. . . . . . . . .
Diagnostic Trouble Code (DTC) P0121
TP System Performance 6E±130. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0122
TP Sensor Circuit Low Voltage 6E±133. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0123
TP Sensor Circuit High Voltage 6E±136. . . . . . . . . .
Diagnostic Trouble Code (DTC) P0131
HO2S Circuit Low Voltage Bank 1
Sensor 1 6E±139. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0132
HO2S Circuit High Voltage Bank 1
Sensor 1 6E±142. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0134
HO2S Circuit Insufficient Activity Bank 1
Sensor 1 6E±145. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0151
HO2S Circuit Low Voltage Bank 2
Sensor 1 6E±148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0152
HO2S Circuit HIGH Voltage Bank 2
Sensor 1 6E±151. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0171
Fuel Trim System Lean Bank 1 6E±154. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0172
Fuel Trim System Rich Bank 1 6E±158. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0174
Fuel Trim System Lean Bank 2 6E±162. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0175
Fuel Trim System Rich Bank 2 6E±166. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0201
Injector 1 Control Circuit 6E±170. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0202
Injector 2 Control Circuit 6E±173. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0203
Injector 3 Control Circuit 6E±176. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0204
Injector 4 Control Circuit 6E±179. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0205
Injector 5 Control Circuit 6E±182. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0206
Injector 6 Control Circuit 6E±185. . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0325
KS Module Circuit 6E±188. . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0327
KS Sensor Circuit 6E±190. . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0336
58X Reference Signal Circuit 6E±193. . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P0337
CKP Sensor Circuit Low Frequency 6E±195. . . . . . .
Diagnostic Trouble Code (DTC) P0341
CMP Sensor Circuit Performance 6E±198. . . . . . . . .
Diagnostic Trouble Code (DTC) P0342
CMP Sensor Circuit Low 6E±202. . . . . . . . . . . . . . . . .

6E±5 ENGINE DRIVEABILITY AND EMISSIONS
Specifications
Tightening Specifications
ApplicationN´mLb Ft.Lb In.
Camshaft Position Sensor Retaining Screw9Ð78
Crankshaft Position Sensor Mounting Bolt10Ð87
EGR Bolt2821Ð
EGR Nut2821Ð
Engine Coolant Temperature Sensor207.7Ð
Fuel Drain Plug2922Ð
Fuel Pressure Regulator Attaching Screw6.5Ð60
Fuel Rail Bolts2518Ð
Fuel Tank Undercover Retaining Bolts3627Ð
Heated Oxygen Sensor4231Ð
Lower Intake Manifold to Engine Block Bolts2518Ð
Lower Intake Manifold to Engine Block Nuts2518Ð
Spark Plugs1813Ð
Throttle Body Mounting Bolts2518Ð
Upper Intake Manifold to Lower Intake Manifold Bolts2518Ð
VSS Retaining Bolt13Ð120
Vehicle Type Specifications
ECAUSTRALIA
THAILAND
SOUTH-EA
ST-ASIA
LATIN
AMERICAGULF
CONTRIES
SAUDI
CHINASOU
TH
AFRI
CA
EXPORTSpecifications
UBSUBSUBSUBSUBSUBS
OBD
O2
SENCATEGRMTATMTATMTATMTATMTMTATOBDSEN
SORAEGR
wI21

wI21

w11

w11

w11

w11

w1

w1

w
wI
w

6E±37 ENGINE DRIVEABILITY AND EMISSIONS
Diagnosis
Strategy-Based Diagnostics
Strategy-Based Diagnostics
The strategy-based diagnostic is a uniform approach to
repair all Electrical/Electronic (E/E) systems. The
diagnostic flow can always be used to resolve an E/E
system problem and is a starting point when repairs are
necessary. The following steps will instruct the technician
how to proceed with a diagnosis:
1. Verify the customer complaint.

To verify the customer complaint, the technician
should know the normal operation of the system.
2. Perform preliminary checks.

Conduct a thorough visual inspection.

Review the service history.

Detect unusual sounds or odors.

Gather diagnostic trouble code information to
achieve an effective repair.
3. Check bulletins and other service information.

This includes videos, newsletters, etc.
4. Refer to service information (manual) system
check(s).

ªSystem checksº contain information on a system
that may not be supported by one or more DTCs.
System checks verify proper operation of the
system. This will lead the technician in an
organized approach to diagnostics.
5. Refer to service diagnostics.
DTC Stored
Follow the designated DTC chart exactly to make an
effective repair.
No DTC
Select the symptom from the symptom tables. Follow the
diagnostic paths or suggestions to complete the repair.
You may refer to the applicable component/system check
in the system checks.
No Matching Symptom
1. Analyze the complaint.
2. Develop a plan for diagnostics.
3. Utilize the wiring diagrams and the theory of
operation.
Call technical assistance for similar cases where repair
history may be available. Combine technician knowledge
with efficient use of the available service information.
Intermittents
Conditions that are not always present are called
intermittents. To resolve intermittents, perform the
following steps:
1. Observe history DTCs, DTC modes, and freezeframe
data.
2. Evaluate the symptoms and the conditions described
by the customer.3. Use a check sheet or other method to identify the
circuit or electrical system component.
4. Follow the suggestions for intermittent diagnosis
found in the service documentation.
Most Tech 2s, such as the Tech II and the
5±8840±0285±0 (Fluke model 87 DVOM), have
data-capturing capabilities that can assist in detecting
intermittents.
No Trouble Found
This condition exists when the vehicle is found to operate
normally. The condition described by the customer may
be normal. Verify the customer complaint against another
vehicle that is operating normally. The condition may be
intermittent. Verify the complaint under the conditions
described by the customer before releasing the vehicle.
1. Re-examine the complaint.
When the Complaint cannot be successfully found or
isolated, a re-evaluation is necessary. The complaint
should be re-verified and could be intermittent as
defined in
Intermittents, or could be normal.
2. Repair and verify.
After isolating the cause, the repairs should be made.
Validate for proper operation and verify that the
symptom has been corrected. This may involve road
testing or other methods to verify that the complaint
has been resolved under the following conditions:

Conditions noted by the customer.

If a DTC was diagnosed, verify a repair by
duplicating conditions present when the DTC was
set as noted in the Failure Records or Freeze
Frame data.
Verifying Vehicle Repair
Verification of the vehicle repair will be more
comprehensive for vehicles with OBD system
diagnostics. Following a repair, the technician should
perform the following steps:
IMPORTANT:Follow the steps below when you verify
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.
1. Review and record the Failure Records and the
Freeze Frame data for the DTC which has been
diagnosed (Freeze Frame data will only be stored for
an A or B type diagnostic and only if the MIL(ºCheck
Engineº lamp) has been requested).
2. Clear the DTC(S).
3. Operate the vehicle within conditions noted in the
Failure Records and Freeze Frame data.
4. Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.

6E±39 ENGINE DRIVEABILITY AND EMISSIONS
The data displayed on the other Tech 2 will appear the
same, with some exceptions. Some Tech 2s will only be
able to display certain vehicle parameters as values that
are a coded representation of the true or actual value. For
more information on this system of coding, refer to
Decimal/Binary/Hexadecimal Conversions. On this
vehicle Tech 2 displays the actual values for vehicle
parameters. It will not be necessary to perform any
conversions from coded values to actual values.
On-Board Diagnostic (OBD)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When
a diagnostic test reports a pass result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The diagnostic test has passed during the current
ignition cycle.

The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The fault identified by the diagnostic test is currently
active.

The fault has been active during this ignition cycle.

The operating conditions at the time of the failure.
Remember, a fuel trim DTC may be triggered by a list of
vehicle faults. Make use of all information available (other
DTCs stored, rich or lean condition, etc.) when
diagnosing a fuel trim fault.
Comprehensive Component Monitor
Diagnostic Operation
Input Components:
Input components are monitored for circuit continuity and
out-of-range values. This includes rationality checking.
Rationality checking refers to indicating a fault when the
signal from a sensor does not seem reasonable, i.e.
Throttle Position (TP) sensor that indicates high throttle
position at low engine loads or MAP voltage. Input
components may include, but are not limited to the
following sensors:

Vehicle Speed Sensor (VSS)

Crankshaft Position (CKP) sensor

Knock Sensor (KS)

Throttle Position (TP) sensor

Engine Coolant Temperature (ECT) sensor

Camshaft Position (CMP) sensor

Manifold Absolute Pressure (MAP) sensor

Mass Air Flow (MAF) sensorIn addition to the circuit continuity and rationality check,
the ECT sensor is monitored for its ability to achieve a
steady state temperature to enable closed loop fuel
control.
Output Components:
Output components are diagnosed for proper response to
control module commands. Components where
functional monitoring is not feasible will be monitored for
circuit continuity and out-of-range values if applicable.
Output components to be monitored include, but are not
limited to, the following circuits:

Idle Air Control (IAC) Motor

Electronic Transmission controls

A/C relays

Cooling fan relay

VSS output

MIL control

Cruise control inhibit
Refer to PCM and Sensors in General Descriptions.
Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors a
vehicle system or component. Conversely, an active test,
actually takes some sort of action when performing
diagnostic functions, often in response to a failed passive
test. For example, the EGR diagnostic active test will
force the EGR valve open during closed throttle decel
and/or force the EGR valve closed during a steady state.
Either action should result in a change in manifold
pressure.
Intrusive Diagnostic Tests
This is any on-board test run by the Diagnostic
Management System which may have an effect on
vehicle performance or emission levels.
Warm-Up Cycle
A warm-up cycle means that engine at temperature must
reach a minimum of 70
C (160
F) and rise at least 22
C
(40
F) over the course of a trip.
Freeze Frame
Freeze Frame is an element of the Diagnostic
Management System which stores various vehicle
information at the moment an emissions-related fault is
stored in memory and when the MIL is commanded on.
These data can help to identify the cause of a fault. Refer
to
Storing And Erasing Freeze Fame Data for more
detailed information.
Failure Records
Failure Records data is an enhancement of the OBD
Freeze Frame feature. Failure Records store the same
vehicle information as does Freeze Frame, but it will store
that information for any fault which is stored in on-board
memory, while Freeze Frame stores information only for
emission-related faults that command the MIL on.

6E±40
ENGINE DRIVEABILITY AND EMISSIONS
Common OBD Terms
Diagnostic
When used as a noun, the word diagnostic refers to any
on-board test run by the vehicle's Diagnostic
Management System. A diagnostic is simply a test run on
a system or component to determine if the system or
component is operating according to specification. There
are many diagnostics, shown in the following list:

Oxygen sensors

Oxygen sensor heaters

EGR

Catalyst monitoring
Enable Criteria
The term ªenable criteriaº is engineering language for the
conditions necessary for a given diagnostic test to run.
Each diagnostic has a specific list of conditions which
must be met before the diagnostic will run. ªEnable
criteriaº is another way of saying ªconditions requiredº.
The enable criteria for each diagnostic is listed on the first
page of the DTC description under the heading
ªConditions for Setting the DTCº. Enable criteria varies
with each diagnostic, and typically includes, but is not
limited to the following items:

engine speed

vehicle speed

ECT

MAF/MAP

barometric pressure

IAT

TP

fuel trim

TCC enabled

A/C on
Trip
Technically, a trip is a key on-run-key off cycle in which all
the enable criteria for a given diagnostic are met, allowing
the diagnostic to run. Unfortunately, this concept is not
quite that simple. A trip is official when all the enable
criteria for a given diagnostic are met. But because the
enable criteria vary from one diagnostic to another, the
definition of trip varies as well. Some diagnostic are run
when the vehicle is at operating temperature, some when
the vehicle first start up; some require that the vehicle be
cruising at a steady highway speed, some run only when
the vehicle is idle; some diagnostics function with the
TCC disables. Some run only immediately following a
cold engine start-up.
A trip then, is defined as a key on-run-key off cycle in
which the vehicle was operated in such a way as to satisfy
the enables criteria for a given diagnostic, and this
diagnostic will consider this cycle to be one trip. However,
another diagnostic with a different set of enable criteria
(which were not met) during this driving event, would not
consider it a trip. No trip will occur for that particular
diagnostic until the vehicle is driven in such a way as to
meet all the enable criteria.
The Diagnostic Executive
The Diagnostic Executive is a unique segment of
software which is designed to coordinate and prioritize
the diagnostic procedures as well as define the protocol
for recording and displaying their results. The main
responsibilities of the Diagnostic Executive are listed as
following:

Commanding the MIL (ªCheck Engineº lamp) on and
off

DTC logging and clearing

Freeze Frame data for the first emission related DTC
recorded

Non-emission related Service Lamp (future)

Operating conditions Failure Records buffer, (the
number of records will vary)

Current status information on each diagnostic
The Diagnostic Executive records DTCs and turns on the
MIL when emission-related faults occur. It can also turn
off the MIL if the conditions cease which caused the DTC
to set.
Diagnostic Information
The diagnostic charts and functional checks are designed
to locate a faulty circuit or component through a process
of logical decisions. The charts are prepared with the
requirement that the vehicle functioned correctly at the
time of assembly and that there are not multiple faults
present.
There is a continuous self-diagnosis on certain control
functions. This diagnostic capability is complemented by
the diagnostic procedures contained in this manual. The
language of communicating the source of the malfunction
is a system of diagnostic trouble codes. When a
malfunction is detected by the control module, a
diagnostic trouble code is set and the Malfunction
Indicator Lamp (MIL) (ªCheck Engineº lamp) is
illuminated.
Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) looks the same as
the MIL you are already familiar with (ªCheck Engineº
lamp). However, OBD requires that the it illuminate under
a strict set of guide lines.
Basically, the MIL is turned on when the PCM detects a
DTC that will impact the vehicle emissions.
The MIL is under the control of the Diagnostic Executive.
The MIL will be turned on if an emissions-related
diagnostic test indicates a malfunction has occurred. It
will stay on until the system or component passes the
same test, for three consecutive trips, with no
emissionsrelated faults.
Extinguishing the MIL
When the MIL is on, the Diagnostic Executive will turn off
the MIL after
three consecutive trips that a ªtest passedº
has been reported for the diagnostic test that originally
caused the MIL to illuminate.
Although the MIL has been turned off, the DTC will remain
in the PCM memory (both Freeze Frame and Failure
Records) until
forty(40) warm-up cycles after no faults
have been completed.

6E±41 ENGINE DRIVEABILITY AND EMISSIONS
If the MIL was set by either a fuel trim or misfire-related
DTC, additional requirements must be met. In addition to
the requirements stated in the previous paragraph, these
requirements are as follows:

The diagnostic tests that are passed must occur with
375 RPM of the RPM data stored at the time the last
test failed.

Plus or minus ten (10) percent of the engine load that
was stored at the time the last failed.

Similar engine temperature conditions (warmed up or
warming up ) as those stored at the time the last test
failed.
Meeting these requirements ensures that the fault which
turned on the MIL has been corrected.
The MIL (ªCheck Engineº lamp) is on the instrument
panel and has the following function:

It informs the driver that a fault affects vehicle emission
levels has occurred and that the vehicle should be
taken for service as soon as possible.

As a bulb and system check, the MIL will come ªONº
with the key ªONº and the engine not running. When
the engine is started, the MIL will turn ªOFF.º

When the MIL remains ªONº while the engine is
running, or when a malfunction is suspected due to a
driveability or emissions problem, a Powertrain
On-Board Diagnostic (OBD ll) System Check must be
performed. The procedures for these checks are given
in On-Board Diagnostic (OBD) System Check. These
checks will expose faults which may not be detected if
other diagnostics are performed first.
DTC Types
Each DTC is directly related to a diagnostic test. The
Diagnostic Management System sets DTC based on the
failure of the tests during a trip or trips. Certain tests must
fail two (2) consecutive trips before the DTC is set. The
following are the four (4) types of DTCs and the
characteristics of those codes:

Type A

Emissions related

Requests illumination of the MIL of the first trip with a
fail

Stores a History DTC on the first trip with a fail

Stores a Freeze Frame (if empty)

Stores a Fail Record

Updates the Fail Record each time the diagnostic
test fails

Type B

Emissions related

ªArmedº after one (1) trip with a fail

ªDisarmedº after one (1) trip with a pass

Requests illumination of the MIL on the
second
consecutive trip
with a fail

Stores a History DTC on the second consecutive trip
with a fail (The DTC will be armed after the first fail)

Stores a Freeze Frame on the second consecutive
trip with a fail (if empty)
Stores a Fail Record when the first test fails (not
dependent on
consecutive trip fails)

Updates the Fail Record each time the diagnostic
test fails

Type C (if the vehicle is so equipped)

Non-Emissions related

Requests illumination of the Service Lamp or the
service message on the Drive Information Center
(DIC) on the
first trip with a fail

Stores a History DTC on the
first trip with a fail


Does not store a Freeze Frame

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic
test fails

Type D (
Type D non-emissions related are not utilized
on certain vehicle applications).

Non-Emissions related

Dose not request illumination of any lamp

Stores a History DTC on the
first trip with a fail


Does not store a Freeze Frame

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic
test fails
IMPORTANT:Only four Fail Records can be stored.
Each Fail Record is for a different DTC. It is possible that
there will not be Fail Records for every DTC if multiple
DTCs are set.
Storing and Erasing Freeze Frame Data and Failure
Records
The data captured is called Freeze Frame data. The
Freeze Frame data is very similar to a single record of
operating conditions. Whenever the MIL is illuminated,
the corresponding record of operating conditions is
recorded to the Freeze Frame buffer.
Data from these faults take precedence over data
associated with any other fault. The Freeze Frame data
will not be erased unless the associated history DTC is
cleared.
Each time a diagnostic test reports a failure, the current
engine operating conditions are recorded in the
Failure
Records
buffer. A subsequent failure will update the
recorded operating conditions. The following operating
conditions for the diagnostic test which failed
typically
include the following parameters:

Air Fuel Ratio

Air Flow Rate

Fuel Trim

Engine Speed

Engine Load

Engine Coolant Temperature

Vehicle Speed

TP Angle

MAP/BARO

Injector Base Pulse Width

Loop Status

6E±42
ENGINE DRIVEABILITY AND EMISSIONS
Intermittent Malfunction Indicator Lamp
In the case of an ªintermittentº fault, the MIL (ªCheck
Engineº lamp) may illuminate and then (after three trips)
go ªOFFº. However, the corresponding diagnostic trouble
code will be stored in the memory. When unexpected
diagnostic trouble codes appear, check for an intermittent
malfunction.
A diagnostic trouble code may reset. Consult the
ªDiagnostic Aidsº associated with the diagnostic trouble
code. A physical inspection of the applicable sub-system
most often will resolve the problem.
Data Link Connector (DLC)
The provision for communication with the control module
is the Data Link Connector (DLC). The DLC is used to
connect to Tech 2. Some common uses of Tech 2 are
listed below:

Identifying stored Diagnostic Trouble Codes (DTCs).

Clearing DTCs.

Performing output control tests.

Reading serial data.
TS24064
Verifying Vehicle Repair
Verification of vehicle repair will be more comprehensive
for vehicles with OBD system diagnostic. Following a
repair, the technician should perform the following steps:
1. Review and record the Fail Records and/or Freeze
Frame data for the DTC which has been diagnosed
(Freeze Frame data will only be stored for an A or B
type diagnostic and only if the MIL has been
requested).
2. Clear DTC(s).
3. Operate the vehicle within conditions noted in the Fail
Records and/or Freeze Frame data.
4. Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
Following these steps are very important in verifying
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.
Reading Diagnostic Trouble Codes Using
A Tech 2
The procedure for reading diagnostic trouble code(s) is to
used a diagnostic Tech 2. When reading DTC(s), follow
instructions supplied by Tech 2 manufacturer.
Clearing Diagnostic Trouble Codes
IMPORTANT:Do not clear DTCs unless directed to do
so by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame
and Failure Record data which may help diagnose an
intermittent fault will also be erased from memory.
If the fault that caused the DTC to be stored into memory
has been corrected, the Diagnostic Executive will begin to
count the ªwarm-upº cycles with no further faults
detected, the DTC will automatically be cleared from the
PCM memory.
To clear Diagnostic Trouble Codes (DTCs), use the
diagnostic Tech 2 ªclear DTCsº. When clearing DTCs
follow instructions supplied by the tool manufacturer.
When Tech 2 is not available, DTCs can also be cleared
by disconnecting
one of the following sources for at least
thirty (30) seconds.
NOTE: To prevent system damage, the ignition key must
be ªOFFº when disconnecting or reconnecting battery
power.

The power source to the control module. Examples:
fuse, pigtail at battery PCM connectors etc.

The negative battery cable. (Disconnecting the
negative battery cable will result in the loss of other
on-board memory data, such as preset radio tuning).

6E±50
ENGINE DRIVEABILITY AND EMISSIONS
Primary System-Based Diagnostic
Primary System-Based Diagnostic
There are primary system-based diagnostics which
evaluate system operation and its effect on vehicle
emissions. The primary system-based diagnostics are
listed below with a brief description of the diagnostic
function:
Oxygen Sensor Diagnosis
The fuel control heated oxygen sensors (Bank 1 HO2S 1
and Bank 2 HO2S 1) are diagnosed for the following
conditions:

Inactive signal (output steady at bias voltage ± approx.
450 mV)

Signal fixed high

Signal fixed low
If the oxygen sensor pigtail wiring, connector or terminal
are damaged, the entire oxygen sensor assembly must
be replaced. DO NOT attempt to repair the wiring,
connector or terminals. In order for the sensor to function
properly, it must have clean reference air provided to it.
This clean air reference is obtained by way of the oxygen
sensor wire(s). Any attempt to repair the wires, connector
or terminals could result in the obstruction of the
reference air and degrade oxygen sensor performance.
Refer to
On-Vehicle Service, Heated Oxygen Sensors.
Fuel Control Heated Oxygen Sensor
The main function of the fuel control heated oxygen
sensors is to provide the control module with exhaust
stream oxygen content information to allow proper fueling
and maintain emissions within mandated levels. After it
reaches operating temperature, the sensor will generate
a voltage, inversely proportional to the amount of oxygen
present in the exhaust gases. The control module uses
the signal voltage from the fuel control heated oxygen
sensors while in closed loop to adjust fuel injector pulse
width. While in closed loop, the PCM can adjust fuel
delivery to maintain an air/fuel ratio which allows the best
combination of emission control and driveability.
HO2S Heater
Heated oxygen sensors are used to minimize the amount
of time required for closed loop fuel control to begin
operation and to allow accurate catalyst monitoring. The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensors (Bank 1 HO2S 1 and
Bank2 HO2S 1) to become active. Oxygen sensor
heaters are required to maintain a sufficiently high
temperature which allows accurate exhaust oxygen
content readings further away from the engine.
Fuel Trim System Monitor Diagnostic
Operation
Fuel Trim System Monitor Diagnostic
Operation
This system monitors the averages of short-term and
long-term fuel trim values. If these fuel trim values stay at
their limits for a calibrated period of time, a malfunction is
indicated. The fuel trim diagnostic compares the
averages of short-term fuel trim values and long-term fuel
trim values to rich and lean thresholds. If either value is
within the thresholds, a pass is recorded. If both values
are outside their thresholds, a rich or lean DTC will be
recorded.
The fuel trim system diagnostic also conducts an intrusive
test. This test determines if a rich condition is being
caused by excessive fuel vapor from the EVAP canister.
In order to meet OBD requirements, the control module
uses weighted fuel trim cells to determine the need to set
a fuel trim DTC. A fuel trim DTC can only be set if fuel trim
counts in the weighted fuel trim cells exceed
specifications. This means that the vehicle could have a
fuel trim problem which is causing a problem under
certain conditions (i.e., engine idle high due to a small
vacuum leak or rough idle due to a large vacuum leak)
while it operates fine at other times. No fuel trim DTC
would set (although an engine idle speed DTC or HO2S
DTC may set). Use a Tech 2 to observe fuel trim counts
while the problem is occurring.
A fuel trim DTC may be triggered by a number of vehicle
faults. Make use of all information available (other DTCs
stored, rich or lean condition, etc.) when diagnosing a fuel
trim fault.
Fuel Trim Cell Diagnostic Weights
No fuel trim DTC will set regardless of the fuel trim counts
in cell 0 unless the fuel trim counts in the weighted cells
are also outside specifications. This means that the
vehicle could have a fuel trim problem which is causing a
problem under certain conditions (i.e. engine idle high due
to a small vacuum leak or rough due to a large vacuum
leak) while it operates fine at other times. No fuel trim
DTC would set (although an engine idle speed DTC or
HO2S DTC may set). Use a Tech 2 to observe fuel trim
counts while the problem is occurring.

6E±53 ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD) System Check

StepActionValue(s)Ye sNo
11. Ignition ªON,º engine ªOFF.º
2. Observe the malfunction indicator lamp (MIL or
ªCheck Engineº lamp).
Is the MIL (ªCheck Engineº lamp)ªON?º
ÐGo to Step 2
Go to No MIL
(ªCheck
Engineº lamp)
21. Ignition ªOFF.º
2. Install a Tech 2.
3. Ignition ªON.º
4. Attempt to display PCM engine data with the Tech 2.
Does the Tech 2 display PCM data?
ÐGo to Step 3Go to Step 8
31. Using the Tech 2 output tests function, select MIL
(ªCheck Engineº lamp) dash lamp control and
command the MIL (ªCheck Engineº lamp) ªOFF.º
2. Observe the MIL (ªCheck Engineº lamp).
Did the MIL (ªCheck Engineº lamp) turn ªOFF?º
ÐGo to Step 4
Go to MIL
(ªCheck
Engineº lamp)
On Steady
4Attempt to start the engine.
Did the engine start and continue to run?
ÐGo to Step 5
Go to Cranks
But Will Not
Run
5Select ªDisplay DTCsº with the Tech 2.
Are any DTCs stored?
ÐGo to Step 6Go to Step 7
6Are two or more of the following DTCs stored? P0107,
P0108, P0113, P0118, P0122, P0123, P0712.?
Ð
Go to
ªMultiple
PCM
Information
Sensor DTCs
Setº
Go to
applicable
DTC table
7Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.
Are the displayed values normal or close to the typical
values?
Ð
Refer
to
Typical
scan data
value
Refer to
indicated
Component
System
Checks
81. Ignition ªOFF,º disconnect the PCM.
2. Ignition ªON,º engine ªOFF.º
3. Check the Class 2 data circuit for an open, short to
ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.
4. If a problem is found, repair as necessary.
Was a problem found?
ÐGo to Step 2Go to Step 9
9Attempt to display PCM data with the Tech 2.
Does the Tech 2 display PCM engine data?
ÐGo to Step 2Go to Step 10
10Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
Powertrain Control Module
(PCM) in On-Vehicle Service.
Is the action complete?ÐGo to Step 2Ð