Electrical wiring diagram 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±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±262
ENGINE DRIVEABILITY AND EMISSIONS
Symptom Diagnosis
Preliminary Checks
Before using this section, perform the ªOn-Board
Diagnostic (OBD) System Checkº and verify all of the
following items:

The powertrain control module (PCM) and malfunction
indicator lamp (MIL) (Service Engine Soon lamp) are
operating correctly.

There are no DTC(s) stored.

Tech 2 data is within normal operating range. Refer to
Typical Scan Data Values.

Verify the customer complaint and locate the correct
symptom in the table of contents. Perform the
procedure included in the symptom chart.
Visual/Physical Check
Several of the symptom procedures call for a careful
visual/physical check. This can lead to correcting a
problem without further checks and can save valuable
time.
This check should include the following items:

PCM grounds for cleanliness, tightness and proper
location.

Vacuum hoses for splits, kinks, and proper
connections, as shown on the ªVehicle Emission
Control Informationº label. Check thoroughly for any
type of leak or restriction.

Air intake ducts for collapsed or damaged areas.

Air leaks at throttle body mounting area, mass air flow
(MAF) sensor and intake manifold sealing surfaces.

Ignition wires for cracking, hardness, and carbon
tracking.

Wiring for proper connections, pinches and cuts.
Intermittents
IMPORTANT:An intermittent problem may or may not
turn on the malfunction indicator lamp (MIL) or store a
DTC. DO NOT use the Diagnostic Trouble Code (DTC)
charts for intermittent problems. The fault must be
present to locate the problem.
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful visual/physical
check for the following conditions:

Poor mating of the connector halves or a terminal not
fully seated in the connector (backed out).

Improperly formed or damaged terminal.

All connector terminals in the problem circuit should be
carefully checked for proper contact tension.

Poor terminal-to-wire connection. This requires
removing the terminal from the connector body to
check.
Road test the vehicle with a J 39200 Digital Multimeter
connected to a suspected circuit. An abnormal voltage
when the malfunction occurs is a good indication that
there is a fault in the circuit being monitored.
Use Tech 2 to help detect intermittent conditions. Tech 2s
have several features that can be used to locate anintermittent condition. Use the following feature to find
intermittent faults:

Using Tech 2's ªFreeze Frameº buffer or ªFailure
Recordsº buffer can aid in locating an intermittent
condition. Review and record the information in the
freeze frame or failure record associated with the
intermittent DTC being diagnosed. The vehicle can be
driven within the conditions that were present when the
DTC originally set.
To check for loss of diagnostic code memory, disconnect
the MAP sensor and idle the engine until the MIL (Service
Engine Soon lamp) comes on. DTC P0107 should be
stored and kept in memory when the ignition is turned
ªOFF.º If not, the PCM is faulty. When this test is
completed, make sure that you clear the DTC P0107 from
memory.
An intermittent MIL (Service Engine Soon lamp) with no
stored DTC may be caused by the following:

Ignition coil shorted to ground and arcing at ignition
wires or plugs.

MIL (Service Engine Soon lamp) wire to PCM shorted
to ground.

Poor PCM grounds. Refer to the PCM wiring
diagrams.
Check for improper installation of electrical options such
as lights, cellular phones, etc. Route ignition coil wiring
away from the ignition coils. Check all wires from the
PCM to the ignition coil for poor connections.
Check for an open diode across the A/C compressor
clutch and check for other open diodes (refer to wiring
diagrams in
Electrical Diagnosis).
If problem has not been found, refer to
PCM Connector
Symptom
tables.

6E±266
ENGINE DRIVEABILITY AND EMISSIONS
Surges and/or Chuggles Symptom

 
StepNo Ye s Value(s) Action
101. Check for proper ignition voltage output with spark
tester J 26792 (ST-125). Refer to
Electric Ignition
System
for procedure.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 11
111. Check for a loose ignition coil ground.
Refer to
Electric Ignition System.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 12
121. Check the ignition coils for cracks or carbon
tracking.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 13
131. Remove the spark plugs and check for wet plugs,
cracks, wear, improper gap, burned electrodes, or
heavy deposits. Refer to
Electronic Ignition
System
.
NOTE: If spark plugs are gas or oil fouled, the cause of
the fouling must be determined before replacing the
spark plugs.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 14
141. Check the injector connections.
2. If any of the injector connectors are connected to an
incorrect cylinder, correct as necessary.
Was a problem found?
ÐVerify repairGo to Step 15
151. Check PCM grounds for the cleanliness, tightness
and proper locations. Refer to the PCM wiring
diagrams in
Electrical Diagnosis.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 16
161. Check MAF sensor connections.
2. If a problem is found, replace the faulty terminals as
necessary. Refer to
Electrical Diagnosis for wiring
repair procedures.
Was a problem found?
ÐVerify repairGo to Step 17
171. Visually/physically check vacuum hoses for splits,
kinks, and proper connections and routing as
shown on the ªVehicle Emission Control
Informationº label.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 18

6E±269 ENGINE DRIVEABILITY AND EMISSIONS
Lack of Power, Sluggish or Spongy Symptom

 
StepNo Ye s Value(s) Action
111. Check the PCM grounds for the cleanliness,
tightness and proper locations. Refer to the PCM
wiring diagrams in
Electrical Diagnosis.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 12
121. Check the exhaust system for possible restriction:

Inspect the exhaust system for damaged or
collapsed pipes.

Inspect the muffler for heat distress or possible
internal failure.

Check for a possible plugged three-way
catalytic converter by checking the exhaust
system back pressure. Refer to
Restricted
Exhaust System Check
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 13
131. Check the torque converter clutch (TCC) for proper
operation. Refer to
4L30-E Transmission
Diagnosis
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 14
141. Check for an engine mechanical problem. Check
for low compression, incorrect or worn camshaft,
loose timing belt, etc. Refer to
Engine Mechanical.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 15
151. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
following:

Visual/physical inspection

Tech 2 data

Freeze Frame data/Failure Records buffer

All electrical connections within a suspected
circuit and/or system.
3. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repair
Contact
Technical
Assistance

6E±272
ENGINE DRIVEABILITY AND EMISSIONS
Rough, Unstable, or Incorrect Idle, Stalling Symptom

StepActionValue(s)Ye sNo
1DEFINITION:
Engine runs unevenly at idle. If severe, the engine or
vehicle may shake. Engine idle speed may vary in
RPM. Either condition may be severe enough to stall
the engine.
Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,
correct the condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
ÐGo to Step 13Go to Step 3
3Was a visual/physical check performed?
ÐGo to Step 4
Go to
Visual/Physic
al Check
41. Check the PCM grounds for cleanliness, tightness
and proper routing. Refer to the PCM wiring
diagrams in
Electrical Diagnosis.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 5
5Observe the long term fuel trim on Tech 2.
Is the long term fuel trim significantly in the negative
range (rich condition)?
ÐGo to Step 6Go to Step 7
61. Check items that can cause the engine to run rich.
Refer to
Diagnostic Aids in DTC P0172 Diagnostic
Support
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 9
7Is the long term fuel trim significantly in the positive
range (lean condition)?
ÐGo to Step 8Go to Step 9
81. Check items that can cause the engine to run lean.
Refer to
Diagnostic Aids in DTC P0171 Diagnostic
Support
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 9
91. Check for incorrect idle speed. Ensure that the
following conditions are present:

The engine is fully warm.

The accessories are ªOFF.º
2. Using Tech 2, monitor the IAC position.
Is the IAC position within the specified values?
Between 10
and 50
counts
Go to Step 11Go to Step 10

6E±282
ENGINE DRIVEABILITY AND EMISSIONS
Cuts Out, Misses Symptom

StepActionValue(s)Ye sNo
1DEFINITION:
Steady pulsation or jerking that follows engine speed;
usually more pronounced as engine load increases.
Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,
correct the condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
ÐGo to Step 13Go to Step 3
3Was a visual/physical check performed?
ÐGo to Step 4
Go to
Visual/Physic
al Check
41. Check the PCM grounds for clearness, tightness
and proper routing. Refer to the PCM wiring
diagrams in
Electrical Diagnosis.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 5
5Observe the long term fuel trim on Tech 2.
Is the long term fuel trim significantly in the negative
range (rich condition)?
ÐGo to Step 6Go to Step 7
61. Check items that can cause the engine to run rich.
Refer to
Diagnostic Aids in DTC P0172 Diagnostic
Support
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 9
7Is the long term fuel trim significantly in the positive
range (lean condition)?
ÐGo to Step 8Go to Step 9
81. Check items that can cause the engine to run lean.
Refer to
Diagnostic Aids in DTC P0171 Diagnostic
Support
.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 9
91. Check for incorrect idle speed. Ensure that the
following conditions are present:

The engine is fully warm.

The accessories are ªoff.º
2. Using Tech 2, monitor the IAC position.
Is the IAC position within the specified values?
Between 5
and 50
counts
Go to Step 11Go to Step 10

6E±286
ENGINE DRIVEABILITY AND EMISSIONS
Hesitation, Sag, Stumble Symptom

 
StepNo Ye s Value(s) Action
101. Check for proper ignition voltage output with spark
tester J 26792 (ST-125). Refer to
Electronic Ignition
System
for the procedure.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 11
111. Check for a loose ignition coil ground.
Refer to
Electronic Ignition System.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 12
121. Check the ignition coils for cracks or carbon
tracking.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 13
131. Remove spark plugs and check for wet plugs,
cracks, wear, improper gap, burned electrodes, or
heavy deposits. Refer to
Electronic Ignition
System
.
NOTE: If spark plugs are gas or oil fouled, the cause of
the fouling must be determined before replacing the
spark plugs.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 14
141. Check the PCM grounds for clearness, tightness
and proper routing. Refer to the PCM wiring
diagrams in Electrical Diagnosis.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 15
151. Check the MAF sensor connections.
2. If a problem is found, replace the faulty terminals as
necessary. Refer to
Electrical Diagnosis for wiring
repair procedures.
Was a problem found?
ÐVerify repairGo to Step 16
161. Visually/physically check vacuum hoses for splits,
kinks, and proper connections and routing as
shown on the ªVehicle Emission Control
Informationº label.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 17

6E±335 ENGINE DRIVEABILITY AND EMISSIONS
General Description
General Description (PCM and
Sensors)
58X Reference PCM Input
The powertrain control module (PCM) uses this signal
from the crankshaft position (CKP) sensor to calculate
engine RPM and crankshaft position at all engine speeds.
The PCM also uses the pulses on this circuit to initiate
injector pulses. If the PCM receives no pulses on this
circuit, DTC P0337 will set. The engine will not start and
run without using the 58X reference signal.
A/C Request Signal
This signal tells the PCM when the A/C mode is selected
at the A/C control head. The PCM uses this to adjust the
idle speed before turning ªONº the A/C clutch. The A/C
compressor will be inoperative if this signal is not
available to the PCM.
Refer to
A/C Clutch Circuit Diagnosis for A/C wiring
diagrams and diagnosis for the A/C electrical system.
Crankshaft Position (CKP) Sensor
The crankshaft position (CKP) sensor provides a signal
used by the powertrain control module (PCM) to calculate
the ignition sequence. The CKP sensor initiates the 58X
reference pulses which the PCM uses to calculate RPM
and crankshaft position.
Refer to
Electronic Ignition System for additional
information.
0013
Camshaft Position (CMP) Sensor and
Signal
The camshaft position (CMP) sensor sends a CMP signal
to the PCM. The PCM uses this signal as a ªsync pulseº totrigger the injectors in the proper sequence. The PCM
uses the CMP signal to indicate the position of the #1
piston during its power stroke. This allows the PCM to
calculate true sequential fuel injection (SFI) mode of
operation. If the PCM detects an incorrect CMP signal
while the engine is running, DTC P0341 will set. If the
CMP signal is lost while the engine is running, the fuel
injection system will shift to a calculated sequential fuel
injection mode based on the last fuel injection pulse, and
the engine will continue to run. As long as the fault is
present, the engine can be restarted. It will run in the
calculated sequential mode with a 1-in-6 chance of the
injector sequence being correct.
Refer to
DTC P0341 for further information.
0014
Engine Coolant Temperature (ECT) Sensor
The engine coolant temperature (ECT) sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream. Low
coolant temperature produces a high resistance of
100,000 ohms at ±40
C (±40
F). High temperature
causes a low resistance of 70 ohms at 130
C (266
F).
The PCM supplies a 5-volt signal to the ECT sensor
through resistors in the PCM and measures the voltage.
The signal voltage will be high when the engine is cold and
low when the engine is hot. By measuring the voltage, the
PCM calculates the engine coolant temperature. Engine
coolant temperature affects most of the systems that the
PCM controls.
Tech 2 displays engine coolant temperature in degrees.
After engine start-up, the temperature should rise steadily
to about 85
C (185
F). It then stabilizes when the
thermostat opens. If the engine has not been run for
several hours (overnight), the engine coolant
temperature and intake air temperature displays should
be close to each other. A hard fault in the engine coolant
sensor circuit will set DTC P0177 or DTC P0118. An
intermittent fault will set a DTC P1114 or P1115.

6E±349 ENGINE DRIVEABILITY AND EMISSIONS

Damage during re-gapping can happen if the gapping
tool is pushed against the center electrode or the
insulator around it, causing the insulator to crack.
When re-gapping a spark plug, make the adjustment
by bending only the ground side terminal, keeping the
tool clear of other parts.

ºHeat shockº breakage in the lower insulator tip
generally occurs during several engine operating
conditions (high speeds or heavy loading) and may be
caused by over-advanced timing or low grade fuels.
Heat shock refers to a rapid increase in the tip
temperature that causes the insulator material to
crack.
Spark plugs with less than the recommended amount of
service can sometimes be cleaned and re-gapped , then
returned to service. However, if there is any doubt about
the serviceability of a spark plug, replace it. Spark plugs
with cracked or broken insulators should always be
replaced.
A/C Clutch Diagnosis
A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of the
PCM when the A/C is selected through the A/C control
switch.
The A/C compressor clutch relay is controlled through the
PCM. This allows the PCM to modify the idle air control
position prior to the A/C clutch engagement for better idle
quality. If the engine operating conditions are within their
specified calibrated acceptable ranges, the PCM will
enable the A/C compressor relay. This is done by
providing a ground path for the A/C relay coil within the
PCM. When the A/C compressor relay is enabled,
battery voltage is supplied to the compressor clutch coil.
The PCM will enable the A/C compressor clutch
whenever the engine is running and the A/C has been
requested. The PCM will not enable the A/C compressor
clutch if any of the following conditions are met:

The throttle is greater than 90%.

The engine speed is greater than 6315 RPM.

The ECT is greater than 119
C (246
F).

The IAT is less than 5
C (41
F).

The throttle is more than 80% open.
A/C Clutch Circuit Purpose
The A/C compressor operation is controlled by the
powertrain control module (PCM) for the following
reasons:

It improvises idle quality during compressor clutch
engagement.

It improvises wide open throttle (WOT) performance.

It provides A/C compressor protection from operation
with incorrect refrigerant pressures.
The A/C electrical system consists of the following
components:

The A/C control head.

The A/C refrigerant pressure switches.

The A/C compressor clutch.

The A/C compressor clutch relay.
The PCM.
A/C Request Signal
This signal tells the PCM when the A/C mode is selected
at the A/C control head. The PCM uses this to adjust the
idle speed before turning on the A/C clutch. The A/C
compressor will be inoperative if this signal is not
available to the PCM.
Refer to
A/C Clutch Circuit Diagnosis for A/C wiring
diagrams and diagnosis for A/C electrical system.
General Description (Exhaust Gas
Recirculation (EGR) System)
EGR Purpose
The exhaust gas recirculation (EGR) system is use to
reduce emission levels of oxides of nitrogen (NOx). NOx
emission levels are caused by a high combustion
temperature. The EGR system lowers the NOx emission
levels by decreasing the combustion temperature.
057RW002
Linear EGR Valve
The main element of the system is the linear EGR valve.
The EGR valve feeds small amounts of exhaust gas back
into the combustion chamber. The fuel/air mixture will be
diluted and combustion temperatures reduced.
Linear EGR Control
The PCM monitors the EGR actual positron and adjusts
the pintle position accordingly. The uses information from
the following sensors to control the pintle position:

Engine coolant temperature (ECT) sensor.

Throttle position (TP) sensor.

Mass air flow (MAF) sensor.
Linear EGR Valve Operation and Results
of Incorrect Operation
The linear EGR valve is designed to accurately supply
EGR to the engine independent of intake manifold
vacuum. The valve controls EGR flow from the exhaust