light ISUZU TROOPER 1998 Service Repair Manual

6E±44
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
No Malfunction Indicator Lamp (MIL)
060RW136
Circuit Description
The ªCheck Engineº lamp (MIL) should always be
illuminated and steady with the ignition ªONº and the
engine stopped. Ignition feed voltage is supplied to the
MIL bulb through the meter fuse. The Engine Control
Module ECM turns the MIL ªONº by grounding the MIL
driver circuit.
Diagnostic Aids
An intermittent MIL may be cause by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:

Inspect the ECM harness and connections for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire
connection, and damaged harness.

If the engine runs OK, check for a faulty light bulb, an
open in the MIL driver circuit, or an open in the
instrument cluster ignition feed.
If the engine cranks but will not run, check for an open
ECM ignition or battery feed, or a poor ECM to engine
ground.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. A ªNo MILº condition accompanied by a no-start
condition suggests a faulty ECM ignition feed or
battery feed circuit.
9. Using a test light connected to B+, probe each of the
ECM ground terminals to ensure that a good ground
is present. Refer to
ECM Terminal End View for
terminal locations of the ECM ground circuits.
12.In this step, temporarily substitute a known good
relay for the ECM relay. The horn relay is nearby,
and it can be verified as ªgoodº simply by honking
the horn. Replace the horn relay after completing
this step.

6E±45 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
No Malfunction Indicator Lamp (MIL)

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Attempt to start the engine.
Does the engine start?
ÐGo to Step 3Go to Step 6
3Check the meter fuse for the instrument cluster ignition
feed circuit.
Is the fuse OK?
ÐGo to Step 4Go to Step 16
4Ignition ªON,º probe the ignition feed circuit at the
cluster connector with a test light to ground.
Is the test light ªON?º
ÐGo to Step 5Go to Step 13
51. Ignition ªOFF.º
2. Disconnect the ECM.
3. Jumper the MIL driver circuit at the ECM connector
to ground.
4. Ignition ªON.º
Is the MIL ªON?º
ÐGo to Step 10Go to Step 11
6Check the ECM ignition feed and battery feed fuses (15
A engine fuse and 15 A ECM fuse).
Are both fuses OK?
ÐGo to Step 7Go to Step 15
71. Ignition ªOFF.º
2. Disconnect the ECM.
3. Ignition ªON.º
4. Probe the ignition feed circuit at the ECM harness
connector with a test light to ground.
Is the test light ªON?º
ÐGo to Step 8Go to Step 12
8Probe the battery feed circuit at the ECM harness
connector with a test light to ground.
Is the test light ªON?º
ÐGo to Step 9Go to Step 14
9Check for a faulty ECM ground connection.
Was a problem found?
ÐVerify repairGo to Step 10
10Check for damaged terminals at the ECM.
Was a problem found?
ÐVerify repairGo to Step 17
11Check for an open MIL driver circuit between the ECM
and the MIL.
Was a problem found?
ÐVerify repairGo to Step 18
12Substitute a known ªgoodº relay for the ECM main
relay.
Was the malfunction fixed?
ÐVerify repairGo to Step 13
13Repair the open in the ignition feed circuit.
Is the action complete?
ÐVerify repairÐ
14Locate and repair the open ECM battery feed circuit.
Is the action complete?
ÐVerify repairÐ

6E±50
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Engine Cranks But Will Not Run

 
StepNo Ye s Value(s) Action
10Refer to Engine Mechanical Diagnosis to diagnose the
following conditions:

Faulty camshaft drive belts

Leaking or sticky valves or rings

Excessive valve deposits

Weak valve springs

Incorrect valve timing

Leaking head gasket
Is the action complete?
ÐVerify repairGo to Step 11
11Observe the ªEngine Speedº data display on the Tech 2
while cranking the engine.
Is the engine RPM indicated? (If the Tech 2 is normally
powered from the cigarette lighter socket, and if the
Tech 2 display goes blank while cranking the engine, it
will be necessary to power the Tech 2 directly from the
vehicle battery.)
ÐGo to Step 12Go to Step 17
121. At the ECM (female) side of the connector
mentioned in step, connect a test light between the
ignition + terminal and one of the injector driver
circuits at the same connector.
2. Ignition ªON.º
3. Observe the test light, and repeat the test for each
injector driver circuit by oscilloscope.
Did the test light stay on when checking any of the 4
injector driver circuits?
ÐGo to Step 13Go to Step 15
131. Ignition ªOFF,º disconnect the ECM.
2. Ignition ªON,º observe the test light.
Is the test light ªON?º
ÐGo to Step 14Go to Step 16
14Locate and repair the short to ground in the injector
driver circuit.
Is the action complete?
ÐVerify repairÐ
15Check for an open injector driver circuit.
Was a problem found?
ÐVerify repairGo to Step 16
16Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairÐ
171. Raise the vehicle and disconnect the CKP sensor
harness.
2. Ignition ªON.º
3. With a test light to ground, probe the harness
ignition feed terminal.
Did the light illuminate?
ÐGo to Step 19Go to Step 18
18Check the ignition feed wire between the sensor and
the ECM for a short to ground or open circuit.
Is the action complete?
ÐVerify repairÐ

6E±51 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Engine Cranks But Will Not Run

 
StepNo Ye s Value(s) Action
191. Ignition ªON.º
2. At the CKP harness connector, connect a test light
between the ignition and ground terminals.
Did the light illuminate?
ÐGo to Step 21Go to Step 20
20Check the sensor ground circuit for an open or short to
voltage.
Is the action complete?
ÐVerify repairÐ
21Check the signal circuit between the sensor and the
ECM for a short to ground, short to voltage, or an open.
Was a problem found?
ÐVerify repairGo to Step 22
22Replace the CKP sensor.
Is the action complete?
ÐVerify repairGo to Step 16

6E±71 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0121 ±AP Sensor Rationality

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Check the Idle SW.
Was the Idle SW circuit open or darmage?
Ð
Replace the
Idle SW
circuit
Go to Step 3
3Observe the AP angle reading on the Tech 2 while
slowly opening the throttle.
Does the AP angle increase steadily and evenly from
the closed throttle value to the wide open throttle
value?Closed
throttle = 0%
Wide open
throttle =
100%
Refer to
Diagnostic
Aids
Go to Step 4
41. Disconnect the AP sensor.
2. Observe the AP sensor reading on the Tech 2.
Is the AP sensor reading near the specified value?
0 VGo to Step 5Go to Step 6
51. Connect a test light between the 5 volt reference
ªJ2º circuit and the AP sensor signal circuit at the AP
sensor harness connector.
2. Observe the AP sensor reading on the Tech 2.
Is the AP sensor reading at the specified value?
5 VGo to Step 8Go to Step 7
6Check the following items:
1. AP signal circuit for a short to voltage.
2. AP sensor ground circuit for high resistance
between the ECM and the AP sensor.
3. AP sensor ground circuit for a poor connection.
4. If a problem is found, repair wiring harness as
necessary.
Was a problem found?
ÐVerify repairGo to Step 9
7Check the following items:
1. AP signal circuit or 5 volt reference ªJ2º circuit for a
poor connection.
2. AP signal circuit or 5 volt reference ªJ2º circuit for
high resistance between the ECM and the AP
sensor.
3. If a problem is found, repair wiring harness as
necessary.
Was a problem found?
ÐVerify repairGo to Step 9
8Replace the AP sensor.
Is the action complete?
ÐVerify repairÐ
9Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairÐ

6E±73 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0122 ±AP Sensor Low Voltage

 
StepNo Ye s Value(s) Action
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 below the specified value?
0.1 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 the ªDTCº info for DTC
P0122.
Does the Tech 2 indicate DTC P0122 failed?
ÐGo to Step 5
Refer to
Diagnostic
Aids
51. Ignition ªOFF.º
2. Disconnect the AP sensor electrical connector.
3. Jumper the 5 volt reference ªJ2º circuit and the AP
signal together at the AP sensor harness connector.
4. Ignition ªON.º
Observe the ªAP Sensorº display on the Tech 2.
Is the ªAP Sensorº at the specified value?
5 VGo to Step 11Go to Step 6
61. Disconnect jumper.
2. Connect a test light between B+ and the AP sensor
signal circuit at the AP sensor harness connector.
Observe the ªAP Sensorº display on the Tech 2.
Is the ªAP Sensorº at the specified value?
5 VGo to Step 7Go to Step 9
71. Ignition ªOFF.º
2. Disconnect the ECM and check the 5 volt reference
ªAº circuit for an open or short to ground.
3. If the 5 volt reference ªJ2º circuit is open or shorted
to ground, repair it as necessary.
Was the 5 volt reference ªJ2º circuit open or shorted to
ground?
ÐVerify repairGo to Step 8
8Check the 5 volt reference ªJ2º circuit for a poor
connection at the ECM and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 13
91. Ignition ªOFF.º
2. Disconnect the ECM, and check the AP signal
circuit for an open, short to ground, or short to the
sensor ground circuit.
3. If the AP sensor signal circuit is open or shorted to
ground, repair it as necessary.
Was the AP signal circuit open or shorted to ground?
ÐVerify repairGo to Step 10
10Check the AP sensor signal circuit for a poor
connection at the ECM and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 13
11Check the AP sensor signal circuit for a poor
connection at the AP sensor and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 12

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

6E±85 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0193 ± RP 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. 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 P0108.
Does the Tech 2 indicate DTC P0108 failed this
ignition?
ÐGo to Step 3
Refer to
Diagnostic
Aids
3Check the RP sensor signal circuit.
Was the RP sensor signal circuit open or darmage?
Ð
Replace the
RP circuit
Go to Step 4
4Probe the sensor ground circuit with a test light to B+.
Is the test light ªON?º
ÐGo to Step 5Go to Step 7
51. Check the RP signal circuit for a short to voltage or a
short to the 5 volt reference ªJ1º circuit.
2. If the RP sensor signal circuit is shorted, repair
circuit as necessary.
Was the RP sensor signal circuit shorted?
ÐVerify repairGo to Step 6
61. Check for a poor sensor ground terminal connection
at the RP sensor electrical connector.
2. If a problem if found, replace the faulty terminal.
Did the terminal require replacement?
ÐVerify repairGo to Step 7
71. Check for a poor sensor ground terminal connection
at the ECM.
2. If a problem is found, replace the faulty terminal.
Did the terminal require replacement?
ÐVerify repairGo to Step 8
81. Check the continuity of the RP sensor ground
circuit.
2. If the RP sensor ground circuit measures over 5
ohms, repair open or poor connection.
Was a condition found and corrected?
ÐVerify repairGo to Step 9
9Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify RepairÐ

6E±89 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P1194 ± RP System 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. Engine is running.
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 P1194.
Does the Tech 2 indicate DTC P1194 failed?
ÐGo to Step 3
Refer to
Diagnostic
Aids
3Connect a test light between B+ and the RP sensor
signal circuit at the RP sensor harness connector.
Is the RP value near the specified value.
5 VGo to Step 4Go to Step 6
41. Ignition ªOFF.º
2. Disconnect the ECM and check the 5 volt reference
ªJ2º circuit for an open or short to ground.
3. If the 5 volt reference ªJ2º circuit is open or shorted
to ground, repair it as necessary.
Was the 5 volt reference ªJ2º circuit open or shorted to
ground?
ÐVerify repairGo to Step 5
5Check the 5 volt reference ªJ2º circuit for a poor
connection at the ECM and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 6
61. Ignition ªOFF.º
2. Disconnect the ECM, and check the RP signal
circuit for an open, short to ground, or short to the
sensor ground circuit.
3. If the RP sensor signal circuit is open or shorted to
ground, repair it as necessary.
Was the RP signal circuit open or shorted to ground?
ÐVerify repairGo to Step 7
7Check the RP sensor signal circuit for a poor
connection at the ECM and the RP sensor; replace the
terminal if necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 8
8Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairGo to Step 9
9Check the 2 way valve.
Was the 2 way valve darmage?
Ð
Replace the 2
way valve
Go to Step 10
10Replace the RPCV.
Is the action complete?
ÐVerify repairGo to Step 11
11Replace the RP sensor.
Is the action complete?
ÐVerify repairÐ

6E±91 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P1195 ± RP System 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. Engine is running.
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 P1195.
Does the Tech 2 indicate DTC P1195 failed?
ÐGo to Step 3
Refer to
Diagnostic
Aids
3Connect a test light between B+ and the RP sensor
signal circuit at the RP sensor harness connector.
Is the RP value near the specified value.
0 VGo to Step 4Go to Step 6
41. Ignition ªOFF.º
2. Disconnect the ECM and check the ground circuit
for an open.
Was the ground circuit open?
ÐVerify repairGo to Step 5
5Check the ground circuit for a poor connection at the
ECM and replace the terminal if necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 6
6Check the RP sensor signal circuit for a poor
connection at the ECM and the RP sensor; replace the
terminal if necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 7
7Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairGo to Step 8
8Check the 2 way valve.
Was the 2 way valve darmage?
Ð
Replace the 2
way valve
Go to Step 9
9Replace the RPCV.
Is the action complete?
ÐVerify repairGo to Step 10
10Replace the RP sensor.
Is the action complete?
ÐVerify repairÐ