1998 ISUZU TROOPER electrical system

6D – 24 ENGINE ELECTRICAL
1 Inspection on Quick Heating Operation
1. Disconnect ECT-sensor connection on the
thermostat housing
Legend
(1) ECT Sensor
(2) EVRV
2. Connect the circuit tester between glow plug and
engine earth.
3. Inspect the following items with starter switch set to
ON position (but do not start the engine).
1) The glow indicator shall light for about 5 sec.
2) The circuit tester shall indicate power supply
voltage for 180 sec.
If above specifications are not satisfied, inspect
wire harness, glow relay and ECT-sensor. If
satisfied, inspect glow plug.2 Inspection on Afterglow Operation
1. Disconnect ECT-sensor connection on the
thermostat housing
Legend
(1) ECT Sensor
(2) EVRV
2. Connect the circuit tester between glow plug and
engine earth.
3. Inspect the following item with the engine started.
1) The circuit tester shall indicate about 12 volts
after 180 seconds of engine start.
•If above specifications are not satisfied, inspect
battery voltage, engine earth, wiring harness,
glow plug, and ECM.
12
060RW166
065RW035
12
060RW166
065RW035
INSPECTION ON QOS4 SYSTEM OPERATION

6E±6
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Removal Procedure 6E±212. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±212. . . . . . . . . . . . . . . . . .
Fuel Filter Cap 6E±213. . . . . . . . . . . . . . . . . . . . . . . . . .
General Description 6E±213. . . . . . . . . . . . . . . . . . . .
Inspection Procedure 6E±213. . . . . . . . . . . . . . . . . .
Fuel Filter 6E±213. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removal and Installation Procedure 6E±213. . . . . .
Fuel Gauge Unit 6E±213. . . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±213. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±214. . . . . . . . . . . . . . . . . .
Fuel Injectors 6E±214. . . . . . . . . . . . . . . . . . . . . . . . . . .
Removal and Installation Procedure 6E±214. . . . . .
Fuel Temperature Sensor 6E±214. . . . . . . . . . . . . . . .
Removal Procedure 6E±214. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±215. . . . . . . . . . . . . . . . . .
Rail Pressure (RP) Sensor 6E±216. . . . . . . . . . . . . . .
Removal Procedure 6E±216. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±216. . . . . . . . . . . . . . . . . .
Fuel Tank 6E±216. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±216. . . . . . . . . . . . . . . . . . . .
Throttle Body (TB) 6E±217. . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±217. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±217. . . . . . . . . . . . . . . . . .
Air Conditioning (A/C) Relay 6E±217. . . . . . . . . . . . . .
Removal Procedure 6E±217. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±217. . . . . . . . . . . . . . . . . .
Exhaust Gas Recirculation (EGR) Vacuum
Switch Valve (VSV) 6E±217. . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±217. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±218. . . . . . . . . . . . . . . . . .
Electronic Vacuum Regurating Valve (EVRV) 6E±219
Removal Procedure 6E±219. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±220. . . . . . . . . . . . . . . . . .
Wiring and Connectors 6E±220. . . . . . . . . . . . . . . . . . .
Wiring Harness Service 6E±220. . . . . . . . . . . . . . . .
Connectors and Terminals 6E±220. . . . . . . . . . . . . .
Wire Harness Repair: Twisted Shielded
Cable 6E±220. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±220. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±221. . . . . . . . . . . . . . . . . .
Twisted Leads 6E±221. . . . . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±221. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±222. . . . . . . . . . . . . . . . . .
Weather-Pack Connector 6E±223. . . . . . . . . . . . . . . . .
Tools Required 6E±223. . . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±223. . . . . . . . . . . . . . . . . . . . Installation Procedure 6E±223. . . . . . . . . . . . . . . . . .
Com-Pack III 6E±224. . . . . . . . . . . . . . . . . . . . . . . . . . .
General Information 6E±224. . . . . . . . . . . . . . . . . . . .
Metri-Pack 6E±224. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tools Required 6E±224. . . . . . . . . . . . . . . . . . . . . . . .
Removal Procedure 6E±224. . . . . . . . . . . . . . . . . . . .
Installation Procedure 6E±224. . . . . . . . . . . . . . . . . .
General Description
(ECM and Sensors) 6E±225. . . . . . . . . . . . . . . . . . . . .
57X Reference ECM Input 6E±225. . . . . . . . . . . . . .
A/C Request Signal 6E±225. . . . . . . . . . . . . . . . . . . .
Crankshaft Position (CKP) Sensor 6E±225. . . . . . .
Camshaft Position (CMP) Sensor and
Signal 6E±225. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Coolant Temperature (ECT) Sensor 6E±225
Electrically Erasable Programmable Read
Only Memory (EEPROM) 6E±225. . . . . . . . . . . . . .
Intake Air Temperature (IAT) Sensor 6E±225. . . . .
Manifold Absolute Pressure (MAP) Sensor 6E±226
Engine Control Module (ECM) 6E±226. . . . . . . . . . .
ECM Function 6E±226. . . . . . . . . . . . . . . . . . . . . . . . .
ECM Components 6E±226. . . . . . . . . . . . . . . . . . . . .
ECM Voltage Description 6E±226. . . . . . . . . . . . . . .
ECM Input/Outputs 6E±226. . . . . . . . . . . . . . . . . . . .
ECM Service Precautions 6E±227. . . . . . . . . . . . . .
Intake Throttle Position (ITP) Sensor 6E±227. . . . .
Transmission Range Switch 6E±227. . . . . . . . . . . . .
Accelerator Position Sensor (AP) 6E±227. . . . . . . .
Aftermarket Electrical and Vacuum
Equipment 6E±227. . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrostatic Discharge Damage 6E±227. . . . . . . . .
General Description (Air Induction) 6E±228. . . . . . . .
Air Induction System 6E±228. . . . . . . . . . . . . . . . . . .
General Description (Fuel Metering) 6E±228. . . . . . .
Deceleration Mode 6E±228. . . . . . . . . . . . . . . . . . . .
Fuel Injector 6E±228. . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Metering System Components 6E±228. . . . . .
A/C Clutch Diagnosis 6E±228. . . . . . . . . . . . . . . . . . . .
A/C Request Signal 6E±228. . . . . . . . . . . . . . . . . . . .
General Description Exhaust Gas
Recirculation (EGR) System 6E±228. . . . . . . . . . . . .
EGR Purpose 6E±228. . . . . . . . . . . . . . . . . . . . . . . . .
Fuse and Relay Panel
(Underhood Electrical Center) RHD 6E±229. . . . . . .
Fuse and Relay Panel
(Underhood Electrical Center) LHD 6E±230. . . . . . .

6E±24
4JX1±TC 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 scan tools, such as the Tech 2 and the DVM, 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
the MIL (ªCheck 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±61 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. Verifies that the fault is present.
3. If DTC P0112 can be repeated only by duplicating
the Failure Records condition, refer to the
Temperature vs. Resistance Value table. The table
may be used to test the IAT sensor at various
temperatures to evaluate the possibility of a
ªshiftedº sensor that may be stored above or below
a certain temperature. If this is the case, replace
the IAT sensor. If the IAT sensor appears to be OK,
the fault is intermittent; refer to
Diagnostic Aids.
Intake Air Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
25772796
15594450
5417280
DTC P0112 ± IAT Sensor Low Voltage

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Ignition ªON,º engine ªOFF.º
2. Using a Tech 2, monitor the intake air temperature
(IAT).
Is the intake air temperature greater than the specified
value?
148
C
(283
F)
Go to Step 4Go to Step 3
31. Ignition ªON,º engine ªOFF.º Review and record
Tech 2 Failure Records data.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor the ª DTCº info for DTC
P0112.
Does the Tech 2 indicate DTC P0112 failed this
ignition?
Ð
Refer to Test
Description
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the IAT sensor electrical connector.
3. Ignition ªON.º
4. Observe the manifold air temperature on the Tech 2.
Is the manifold air temperature below the specified
value?
±38
C
(±36
F)
Go to Step 6Go to Step 5
51. Ignition ªOFF.º
2. Disconnect the ECM electrical connectors.
3. Check the IAT sensor signal circuit for a short to
ground.
Is the IAT sensor signal circuit shorted to ground?
ÐVerify repairGo to Step 7
6Replace the IAT sensor.
Is the action complete?
ÐVerify repairÐ
7Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairÐ

6E±63 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. Verifies that the fault is present.
3. If DTC P0113 can be repeated only by duplicating
the Failure Records conditions, refer to the
ªTemperature vs. Resistance Valuesº table. The
table may be used to test the MAT sensor at various
temperatures to evaluate the possibility of a
ªshiftedº sensor that may be open above or below a
certain temperature. If this is the case, replace the
MAT sensor. If the MAT sensor appears to be OK,
the fault is intermittent; refer to
Diagnostic Aids.
Manifold Air Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
25772796
15594450
5417280
DTC P0113 ±IAT Sensor Circuit High Voltage

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Ignition ªON,º engine ªOFF.º Observe the ªIntake Air
Tempº display on the Tech 2.
Is the ªIntake Air Tempº below the specified value?
±38
C
(±36
F)
Go to Step 4Go to Step 3
31. Ignition ªON,º engine ªOFF.º
2. Review and record Tech 2 Failure Records data
parameters.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor ª DTCº info for DTC P0113.
Does the Tech 2 indicate DTC P0113 failed?
Ð
Refer to Test
Description
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the IAT sensor electrical connector.
3. Jumper the IAT signal circuit and the sensor ground
circuit together at the IAT sensor harness
connector.
4. Ignition ªON.º
5. Observe the ªIntake Air Tempº display on the Tech
2.
Is the ªIntake Air Tempº at the specified value?
140
C
(284
F)
Go to Step 6Go to Step 5
51. Jumper the IAT signal circuit at the IAT sensor
harness connector to chassis ground.
2. Observe the ªIntake Air Tempº display on the Tech
2.
Is the ªIntake Air Tempº at the specified value?
140
C
(284
F)
Go to Step 7Go to Step 8
6Check for poor connections at the IAT sensor and
replace terminals if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 10
71. Ignition ªOFF.º
2. Disconnect the ECM, and check the IAT sensor
ground circuit for an open.
3. If the IAT sensor ground circuit is open, repair it as
necessary.
Was the IAT sensor ground circuit open?
ÐVerify repairGo to Step 9

6E±66
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Engine Coolant Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
25772796
15594450
DTC P0117 ± ECT Sensor Low Voltage

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Ignition ªON,º engine ªOFF.º
2. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº below the specified value?
139
C
(282
F)
Go to Step 4Go to Step 3
31. Ignition ªON,º engine ªOFF.º
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor ª DTCº info for DTC P0117.
Does the Tech 2 indicate DTC P0117 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Disconnect the ECT sensor electrical connector.
2. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº at the specified value?
±39
C
(±38
F)
Go to Step 6Go to Step 5
51. Ignition ªOFF.º
2. Disconnect the ECM and check the ECT signal
circuit for a short to ground or a short to the sensor
ground circuit.
3. If the ECT signal circuit is shorted. repair it as
necessary.
Was the ECT signal circuit shorted to ground?
ÐVerify repairGo to Step 7
6Replace the ECT sensor.
Is the action complete?
ÐVerify repairÐ
7Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairÐ

6E±68
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Verifies that the fault is present.
3. If DTC P0118 can be repeated only by duplicating
the Failure Records conditions, refer to the
ªTemperature vs. Resistance Valueº table. The
table may be used to test the ECT sensor at various
temperatures to evaluate the possibility of a
ªshiftedº sensor that may be shorted above or below
a certain temperature. If this is the case, replace
the ECT sensor. If the ECT sensor appears to be
OK, the fault is intermittent; refer to
Diagnostic Aids.
Engine Coolant Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
80176332
25772796
15594450
DTC P0118 ± ECT Sensor High Voltage

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Ignition ªON,º engine ªOFF.º
2. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº below the specified value?
±39
C
(±38
F)
Go to Step 4Go to Step 3
31. Ignition ªON,º engine ªOFF.º
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor the ª DTCº info for DTC
P0118.
Does the Tech 2 indicate DTC P0118 failed?
Ð
Refer to Test
Description
Refer to
Diagnostic
Aids
41. Disconnect the ECT sensor electrical connector.
2. Jumper the ECT signal circuit and the sensor
ground circuit together at the ECT sensor harness
connector.
3. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº at the specified value?
140
C
(284
F)
Go to Step 6Go to Step 5
51. Jumper the ECT signal circuit at the ECT sensor
harness connector to chassis ground.
2. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº at the specified value?
140
C
(284
F)
Go to Step 7Go to Step 8
6Check for poor connections at the ECT sensor and
replace terminals if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 10
71. Ignition ªOFF.º
2. Disconnect the ECM, and check the ECT sensor
ground circuit for an open.
3. If the ECT sensor ground circuit is open, repair it as
necessary.
Was the ECT sensor ground circuit open?
ÐVerify repairGo to Step 9

6E±76
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0123 ± AP Sensor High Voltage

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Check the AP sensor signal circuit.
Was the AP sensor signal circuit open or darmage?
Ð
Replace the
APS circuit
Go to Step 3
31. Ignition ªON,º engine ªOFF.º
2. With the throttle closed, observe the ªAP Sensorº
display on the Tech 2.
Is the ªAP Sensorº above the specified value?
4.5 VGo to Step 5Go to Step 4
41. Ignition ªON,º engine ªOFF.º
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor ªDTCº info for DTC P0123.
Does the Tech 2 indicate DTC P0123 failed.
ÐGo to Step 5
Refer to
Diagnostic
Aids
51. Disconnect the AP sensor electrical connector.
2. Observe the ªAP Sensorº display on the Tech 2.
Is the ªAP Sensorº near the specified value?
0 VGo to Step 6Go to Step 7
6Probe the sensor ground circuit at the AP sensor
harness connector with a test light connected to B+.
Is the test light ªON?º
ÐGo to Step 8Go to Step 11
71. Ignition ªOFF,º disconnect the ECM.
2. Ignition ªON,º engine ªOFF.º
3. Check for a short to voltage on the AP sensor signal
circuit.
4. If the AP sensor signal circuit is shorted, repair it as
necessary.
Was the AP sensor signal circuit shorted?
ÐVerify repairGo to Step 13
81. Ignition ªON.º
2. Monitor the ªAP Sensorº Tech 2 display while
disconnecting each of the components that share
the 5 volt reference ªJ2º circuit (one at a time).
3. If the ªAP Sensorº Tech 2 display changes, replace
the component that caused the display to change
when disconnected.
Does disconnecting any of these components cause
the ªAP Sensorº display to change?
ÐVerify repairGo to Step 9
91. Ignition ªOFF,º disconnect the ECM.
2. Ignition ªON,º engine ªOFF.º
3. Check for a short to B+ on the 5 volt reference ªAº
circuit.
4. If the 5 volt reference ªJ2º circuit is shorted, repair it
as necessary.
Was the 5 volt reference ªJ2º circuit shorted?
ÐVerify repairGo to Step 10
10Check for poor electrical connections at the AP sensor
and replace terminals if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 12