1998 ISUZU TROOPER diagram

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±319 ENGINE DRIVEABILITY AND EMISSIONS
Fuel Pump Relay
Removal Procedure
1. Remove the fuse and relay box cover from under the
hood.
2. Consult the diagram on the cover to determine which
is the correct relay.
3. Insert a small screwdriver into the catch slot on the
forward side of the fuel pump relay.

The screwdriver blade will release the catch inside.
T321092
4. Pull the relay straight up and out of the fuse and relay
box.
TS23976R
Installation Procedure
1. Insert the relay into the correct place in the fuse and
relay box with the catch slot facing forward.
2. Press down until the catch engages.

An audible ªclickº will be heard.
T321092
3. Install the fuse and relay box cover.
Fuel Rail Assembly
Removal Procedure
NOTE:

Do not attempt to remove the fuel inlet fitting on the
fuel rail. It is staked in place. Removing the fuel inlet
fitting will result in damage to the fuel rail or the
internal O-ring seal.

Use care when removing the fuel rail assembly in
order to prevent damage to the injector electrical
connector terminals and the injector spray tips.

Fittings should be capped and holes plugged during
servicing to prevent dirt and other contaminants from
entering open lines and passages.

6E±325 ENGINE DRIVEABILITY AND EMISSIONS
Spark Plug Gap Check

Check the gap of all spark plugs before installation.

Use a round wire feeler gauge to ensure an accurate
check.

Plugs installed with the wrong gap can cause poor
engine performance and excessive emissions.
Installation Procedure
NOTE: The plug must thread smoothly into the cylinder
head and be fully seated. Use a thread chaser if
necessary to clean the threads in the cylinder head.
Cross-threading or failure to fully seat the spark plug can
cause plug overheating, exhaust blow-by gas, or thread
damage. Do not overtighten the spark plugs. Over
tightening can cause aluminum threads to strip.
1. Install the spark plug in the engine. Use the
appropriate spark plug socket.
Tighten

Tighten the spark plug to 18 N´m (13 lb ft.).
2. Install the ignition coil and spark plug boot over the
spark plug.
014RW108
3. Secure the ignition coil to the rocker cover with two
screws.
014RW091
4. Connect the electrical connector at the ignition coil.
5. Connect the negative battery cable.
Catalytic Converter
Removal and Installation Procedure
Refer to Engine Exhaust in Engine.
Air Conditioning Relay
Removal Procedure
1. Remove the fuse and relay box cover from under the
hood.
2. Consult the diagram on the cover to determine which
is the correct relay.
3. Insert a small screwdriver into the catch slot on the
forward side of the fuel pump relay.

The screwdriver blade will release the catch inside.
T321092

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.