check engine light ISUZU TROOPER 1998 Service Owners Manual

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

6E±124
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0342 ÐCMP Sensor No Signal

 
StepNo Ye s Value(s) Action
81. Turn the ignition ªOFF.º
2. Disconnect the ECM and connect a DVM to monitor
voltage on the camshaft position signal circuit at the
ECM connector.
3. Ignition ªON.º
4. Monitor the voltage display on the DVM while
repeatedly touching the CMP sensor signal circuit
at the CMP sensor connector with a test light to
ground.
Does the DVM voltage display switch between 0 and
approximately 5 volts when the test light is touched to
the CMP sensor signal circuit?
ÐGo to Step 12Go to Step 9
91. Ignition ªOFF.º
2. Leave the ECM disconnected.
3. Ignition ªON.º
4. Probe the camshaft position signal circuit at the
ECM connector with a test light to B+.
5. If the test light is ªON,º locate and repair the short to
ground in the camshaft position input signal circuit.
Was either circuit shorted to ground?
ÐVerify repairGo to Step 10
101. Ignition ªOFF.º
2. Leave the ECM disconnected.
3. Ignition ªON.º
4. Probe the camshaft position signal circuit with a test
light to ground.
5. If the test light is ªON,º locate and repair the short to
voltage in the camshaft position input signal circuit.
Was the test light ªONº?
ÐVerify repairGo to Step 11
111. Ignition ªOFF,º disconnect the ECM (leave the CMP
sensor disconnected).
2. Ignition ªON,º check the following circuit:

The CMP sensor signal circuit for an open.
3. If a problem is found, repair it as necessary.
Was a problem found?
ÐVerify repairÐ
121. Ignition ªON.º
2. Remove the CMP sensor from the engine front
cover (leave the sensor wiring connected).
3. Place a magnet on the CMP sensor. If you use a
magnet that is too small to cover the face of the
sensor, test on every part of the sensor face
because only a small area will respond to this test.
Does the DVM display a voltage near the specified
value?
0 VGo to Step 14Go to Step 13
13Replace the camshaft position sensor.
Is the action complete?
ÐVerify repairÐ
141. Reinstall the CMP sensor to the engine front cover.
2. Observe the DVM connected to monitor voltage on
the camshaft position signal circuit while cranking
the engine.
Does the voltage toggle between the specified values?
4-0 VGo to Step 15Go to Step 16

6E±153 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
10. To avoid backprobing the VSS and possibly
damaging a seal or terminal, the VSS output can be
tested at the point where the transmission harness
connected to the engine harness. The green 16-way
connector is adjacent to a blue 16-way connector,
and it can be easily accessed by removing the air
cleaner assembly. The green 16-way connector is
separated, and battery voltage is applied to the VSS
through the yellow wire at one corner of the
connector. The VSS output can be monitored with a
DVM connected to the blue wire with a black tracer.
The two wires are next to each other in the 16-way
connector . The test connections are made on the
transmission side of the connector, the side that is
not clipped to the body sheetmetal.11. The speedometer-to-ECM VSS signal wire is
spliced to a wire leading to the cruise control
module. If a short to ground or voltage is found
between the ECM and speedometer, it could be
located between the splice and the cruise control
module.
DTC P0502 ±VSS No Signal

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Does the speedometer work?ÐGo to Step 10Go to Step 3
31. Disconnect the VSS connector.
2. Ignition ªON.º
3. Using a test light to battery +, probe the connector
ground wire.
Did the light illuminate?
ÐGo to Step 5Go to Step 4
4Repair the sensor ground.
Is the action complete?
ÐVerify repairÐ
51. Ignition ªON,º sensor disconnected.
2. Using a DVM, measure at the VSS connector
between ground and voltage supply.
Was the measurement near the specified value?
Battery
voltage
Go to Step 7Go to Step 6
6Repair the open or short to ground which may have
blown the meter fuse.
Is the action complete?
ÐVerify repairÐ
71. Ignition ªON,º VSS disconnected.
2. Using a DVM, measure at the VSS connector
between ground and the blue/black wire from the
speedometer.
Was the measurement near the specified value?
7.5-8 VGo to Step 9Go to Step 8
8Check for an open or short circuit between the
speedometer and the VSS.
Was an open or short circuit located?
ÐVerify repairGo to Step 9
9Replace the VSS.
Is the action complete?
ÐVerify repairGo to Step 10
10Replace the speedometer.
Is the action complete?
ÐVerify repairGo to Step 11

6E±159 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0562 (Flash DTC 35)
System Voltage Too Low
Circuit Description
The engine control module (ECM) monitors the system
voltage on the ignition feed terminals to the ECM. A
system voltage DTC will set whenever the voltage is
above a calibrated value.
Action Taken When the DTC Sets

The ECM will not illuminate the malfunction indicator
lamp (MIL).

The ECM will store as Failure Records only conditions
which were present when the DTC was set. This
information will not be stored as Freeze Frame data.
Conditions for Clearing the MIL/DTC

DTC P0563 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the ECM battery
feed.
Diagnostic Aids
If the DTC sets when an accessory is operated, check for
a poor connection or defective accessory.
DTC P0562 ± System Voltage Too Low

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Using a DVM, measure the battery voltage at the
battery.
Is the battery voltage greater than the specified value?
11.5 VGo to Step 3
Charge
battery, then
go to
Step 3
31. Install a Tech 2.
2. Select ªIgnition Voltsº on the Tech 2.
3. Start the engine and raise the engine speed to the
specified value.
4. Load the electrical system by turning on the
headlights, high blower, etc.
Is the ignition voltage approximately equal to the
specified value?
2000 RPM
12.8-14.1 V
Go to Step 4
Go to
Starting/
Charging
41. Ignition ªOFF.º
2. Disconnect the ECM connector at the ECM.
3. Using a DVM, measure the battery voltage at the
ECM connector.
Is it approximately equal to battery voltage?
Ð
Check for
excessive
current draw
with ignition
ªOFF,º engine
ªOFF.º
Go to Step 5
51. Check for faulty connections at the ECM harness
terminals.
2. Repair as necessary.
Was a repair necessary?
ÐVerify repairGo to Step 6
6Check for an open battery feed circuit to the ECM.
Is the action complete?
ÐVerify repairGo to Step 7
7Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairÐ

6E±176
4JX1±TC 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 (ECM) and
malfunction indicator lamp (MIL) (CHECK ENGINE
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:

ECM 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.

Injector 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 Digital Multimeter
(5-8840-0285-0) 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 a scan tool to help detect intermittent conditions. The
scan tools have several features that can be used to
locate an intermittent condition. Use the following feature
to find intermittent faults:
Using a Tech±2 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 (CHECK
ENGINE lamp) comes on. DTC P0107 should be stored
and kept in memory when the ignition is turned ªOFF.º If
not, the ECM is faulty. When this test is completed, make
sure that you clear the DTC P0107 from memory.
An intermittent MIL (CHECK ENGINE lamp) with no
stored DTC may be caused by the following:

MIL (CHECK ENGINE lamp) wire to ECM shorted to
ground.

Poor ECM grounds. Refer to the ECM wiring
diagrams.
Check for improper installation of electrical options such
as lights, cellular phones, etc.
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
ECM Connector
Symptom
tables.

6E±196
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
QOS System Doesn't Work

StepActionValue(s)Ye sNo
1Was OBD System check performed?
ÐGo to Step 2
Go to OBD
System
Check
2Check glawplug indicator light. If bulb is broken,
replace.
Was a problem found?
ÐVerify repairGo to Step 3
31. Connect a circuit tester between glawplug & engine
ground.
2. With ignition on and engine off, check if the glaw
indicator and circuit tester indicate power voltage
for 9 to 13 sec. If not indicated, repair terminal & wire
harness.
Was repair needed?
ÐVerify repairGo to Step 4
41. Connect a circuit tester between glawplug and
engine ground.
2. With engine on, check if voltage continues for 180
sec. If not, inspect and repair glaw relay.
Was repair needed?
ÐVerify repairGo to Step 5
51. Remove the glawplug, and if damaged, replace.
2. Check glawplug resistance.
Was resistance as specified?
0.8 ± 1
Go to Step 7Go to Step 6
6Replace glawplug.
Was measure completed?
ÐVerify repairGo to Step 7
71. 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 butter

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