light ISUZU TROOPER 1998 Service Repair Manual

6E±98
ENGINE DRIVEABILITY AND EMISSIONS
Exhaust Gas Recirculation (EGR) System Check

StepActionValue(s)Ye sNo
1Check the EGR valve for looseness.
Is the EGR valve Loose?
ÐGo to Step 2Go to Step 3
2Tighten the EGR valve.
Is the action complete?
ÐVerify repairÐ
31. Place the transmission selector in Park or Neutral.
2. Start the engine and idle until warm.
3. Using Tech 2, command EGR ª50% ON.º
Does the engine idle rough and lose RPMs?
Ð
EGR system
working
properly. No
problem
found.
Go to Step 4
41. Engine ªOFF.º
2. Ignition ªON.º
3. Using a test light to ground, check the EGR harness
between the EGR valve and the ignition feed.
Does the test light illuminate?
ÐGo to Step 6Go to Step 5
5Repair the EGR harness ignition feed.
Was the problem corrected?
ÐVerify repairGo to Step 6
61. Remove the EGR valve.
2. Visually and physically inspect the EGR valve
pintle, valve passages and adapter for excessive
deposits, obstructions or any restrictions.
Does the EGR valve have excessive deposits,
obstructions or any restrictions?
ÐGo to Step 7Go to Step 8
7Clean or replace EGR system components as
necessary.
Was the problem corrected?
ÐVerify repairGo to Step 8
81. Ground the EGR valve metal case to battery (±).
2. Using Tech 2, command EGR ªONº and observe the
EGR valve pintle for movement.
Does the EGR valve pintle move according to
command?
ÐGo to Step 9
Go to DTC
P1406 chart
91. Remove the EGR inlet and outlet pipes from the
intake and exhaust manifolds.
2. Visually and physically inspect manifold EGR ports
and EGR inlet and outlet pipes for blockage or
restriction caused by excessive deposits or other
damage.
Do the manifold EGR ports or inlet and outlet pipes
have excessive deposits, obstructions, or any
restrictions?
ÐGo to Step 10
EGR system
working
properly. No
problem
found.
10Clean or replace EGR system components as
necessary.
Is the action complete?
ÐVerify repairÐ

6E±101 ENGINE DRIVEABILITY AND EMISSIONS
PCM Diagnostic Trouble Codes
The following table lists the diagnostic trouble codes
supported by this vehicle application. If any DTCs not
listed here are displayed by a Tech 2, the Tech 2 data may
be faulty; notify the Tech 2 manufacturer of any DTCs
displayed that are not included in the following table.
A - Emission related P-code, check engine light on as
soon as a failure detected.
B - Emission related P-code, check engine light on if a
failure detected in two consecutive trips.
C - Non emission related P-code, check engine light on
if a failure detected in one trip.
D - Non emission related P-code, no check engine
light, but P-code will be set if a failure detected.
X - Do not check.

6E±106
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0101 ± MAF System Performance

 
StepNo Ye s Value(s) Action
61. Ignition ªON,º engine ªOFF.º
2. Review the Freeze Frame and/or Failure Records
data for this DTC and note parameters.
3. Ignition ªOFFº for 15 seconds.
4. Start the engine and operate the vehicle within the
conditions required for this diagnostic to run, and as
close to the conditions recorded in Freeze Frame
/Failure Records possible. (Special operating
conditions that need to be met before the PCM will
run this diagnostic (where applicable) are listed in
ªConditions for Setting the DTCº).
5. Using the Tech 2, select ªDTC,º then enter the DTC
number which was set.
Does the Tech 2 indicate that this diagnostic failed this
ignition?
ÐGo to Step 7
Refer to
Diagnostic
Aids
71. Check for the following conditions:

Objects blocking the MAF sensor inlet screen;

Intake manifold vacuum leaks;

Vacuum leaks at throttle body;

Vacuum leaks EGR value flange and pipes.

Crankcase ventilation valve faulty, missing, or
incorrectly installed.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo toStep 8
81. Ignition ªOFF.º
2. Disconnect the MAF sensor connector.
3. Ignition ªON,º engine ªOFF.º
4. Using DVM 5-8840-0285-0, measure voltage
between the MAF sensor signal circuit and chassis
ground.
Is the voltage near the specified value?
5 VGo to Step 9Go toStep 10
9Connect a test light (5-8840-0607-0) between the MAF
sensor ignition feed and ground circuits at the MAF
sensor harness connector.
Is the test light ªON?º
ÐGo to Step 13Go toStep 12
10Is the voltage less than the specified value?4.5 VGo to Step 13Go toStep 11
111. Ignition ªOFF,º disconnect the PCM.
2. Ignition ªON,º engine ªOFF.º
3. Measure voltage between the MAF signal circuit
and ground.
Does the voltage measure near the specified value?
0 VGo to Step 13Go toStep 12
12Connect a test light (5-8840-0607-0) between the MAF
sensor ignition feed circuit and chassis ground.
Is the test light ªON?º
ÐGo to Step 13Go toStep 7
131. Check for a poor connection at the MAF sensor.
2. If a poor connection is found, replace faulty
terminal(s). Refer to
Repair Procedures in
Electrical Diagnosis (8A Cell 5).
Was a poor connection found?ÐVerify repairSolved

6E±108
ENGINE DRIVEABILITY AND EMISSIONS
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. This step verifies that the problem is present at idle.4. A voltage reading of less than 4 or over 5 volts at the
MAF sensor signal circuit indicates a fault in the
wiring or a poor connection.
5. This verifies that ignition feed voltage and a good
ground are available at the MAF sensor.
DTC P0102 ± MAF Sensor Circuit Low Frequency

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Start the engine.
2. With the engine idling, monitor ªMAF Frequencyº
display on the Tech 2.
Is the ªMAF Frequencyº below the specified value?
3 g/SecGo to Step 4Go to Step 5
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 ªDTCº info for DTC P0102.
Does the Tech 2 indicate DTC P0102 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the MAF sensor connector.
3. Ignition ªON,º engine ªOFF.º
4. Using a DVM, measure voltage between the MAF
sensor signal circuit and battery ground.
Is the voltage near the specified value?
5 VGo to Step 5Go to Step 8
5Connect a test light between the MAF sensor ignition
feed and ground circuits at the MAF sensor harness
connector.
Is the test light ªON?º
ÐGo to Step 13Go to Step 6
6Connect a test light between the MAF sensor ignition
feed circuit and battery ground.
Is the test light ªON?º
ÐGo to Step 12Go to Step 7
71. Check for a poor connection at the MAF sensor.
2. If a poor connection is found, replace the faulty
terminal(s).
Was a poor connection found?
ÐVerify repairGo to Step 11
81. Ignition ªOFF.º
2. Disconnect the MAF sensor.
3. Disconnect the PCM connector for the MAF signal
circuit.
4. Ignition ªON,º engine ªOFF.º
5. With the DVM, measure the voltage between the
MAF signal terminal at the PCM and battery ground.
Is the voltage under the specified value?
4 VGo to Step 9Go to Step 10

6E±113 ENGINE DRIVEABILITY AND EMISSIONS
and wiring harnesses related to the sensor. A change
in the display will indicate the location of the fault.
If DTC P0107 cannot be duplicated, the information
included in the Failure Records data can be useful indetermining vehicle mileage since the DTC was last set.
If it is determined that the DTC occurs intermittently,
performing the DTC P0107 Diagnostic Chart may isolate
the cause of the fault.
DTC P0107 ± MAP Sensor Circuit 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. With the throttle closed, observe the MAP value
displayed on the Tech 2.
Is the MAP value near the specified value?
11 kPa at sea
level
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 ªSpecific DTCº info for DTC
P0107.
Does the Tech 2 indicate DTC P0107 failed?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the MAP sensor electrical connector.
3. Jumper the 5 volt reference ªAº circuit and the MAP
signal together at the MAP sensor harness
connector.
4. Ignition ªON.º
5. Observe the MAP value displayed on the Tech 2.
Is the MAP value near the specified value?
5 V 104 kPaGo to Step 10Go to Step 5
51. Disconnect the jumper.
2. Connect a test light between B+ and the MAP
sensor signal circuit at the MAP sensor harness
connector.
3. Observe the MAP value displayed on the Tech 2.
Is the MAP value near the specified value.
5 V 104 kPaGo to Step 6Go to Step 8
61. Ignition ªOFF.º
2. Disconnect the PCM and check the 5 volt reference
ªAº circuit for an open or short to ground.
3. If the 5 volt reference ªAº circuit is open or shorted to
ground, repair it as necessary.
Was the 5 volt reference ªAº circuit open or shorted to
ground?
ÐVerify repairGo to Step 7
7Check the 5 volt reference ªAº circuit for a poor
connection at the PCM and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 11
81. Ignition ªOFF.º
2. Disconnect the PCM, and check the MAP signal
circuit for an open, short to ground, or short to the
sensor ground circuit.
3. If the MAP sensor signal circuit is open or shorted to
ground, repair it as necessary.
Was the MAP signal circuit open or shorted to ground?
ÐVerify repairGo to Step 9

6E±116
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0108 ± MAP 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
21. If the engine idle is rough, unstable or incorrect,
repair the idle problem before using this chart. Refer
to
Symptoms section.
2. With the engine idling, note the MAP value on the
Tech 2.
Is the MAP reading above the specified value?
90 kPaGo 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 ªSpecific DTCº info for DTC
P0108.
Does the Tech 2 indicate DTC P0108 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnected the MAP sensor electrical connector.
3. Ignition ªON.º
4. Note the MAP sensor voltage displayed on the Tech
2.
Is the MAP sensor voltage at the specified value?
0.0 V 11 kPaGo to Step 5Go to Step 6
5Probe the sensor ground circuit with a test light to B+.
Is the test light ªON?º
ÐGo to Step 7Go to Step 9
61. Check the MAP signal circuit for a short to voltage or
a short to the 5 volt reference ªAº circuit.
2. If the MAP sensor signal circuit is shorted, repair
circuit as necessary.
Was the MAP sensor signal circuit shorted?
ÐVerify repairGo to Step 11
71. Check for a poor sensor ground terminal connection
at the MAP sensor electrical connector.
2. If a problem if found, replace the faulty terminal.
Did the terminal require replacement?
ÐVerify repairGo to Step 8
8Check for a plugged or leaking vacuum supply to the
MAP sensor.
Is the vacuum supply plugged or leaking?
ÐVerify repairGo to Step 12
91. Check for a poor sensor ground terminal connection
at the PCM.
2. If a problem is found, replace the faulty terminal.
Did the terminal require replacement?
ÐVerify repairGo to Step 10
101. Check the continuity of the MAP sensor ground
circuit.
2. If the MAP sensor ground circuit measures over 5
ohms, repair open or poor connection.
Was a condition found and corrected?
ÐVerify repairGo to Step 11

6E±131 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0121 ±TP System Performance

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 not running.
2. Observe the MAP reading on the Tech 2.
Is the MAP reading less than the specified value?
65 kPaGo to Step 3Go to Step 6
31. Disconnected the MAP sensor.
2. Connect a test light between the 5 volt reference ªAº
circuit and the MAP signal circuit at the MAP sensor
harness connector.
3. Observe the MAP reading on the Tech 2.
Is the MAP reading less than the specified value?
65 kPaGo to Step 5Go to Step 4
41. Check the MAP signal circuit between the PCM and
the MAP sensor for an open, short to ground, or
short to the MAP ground circuit.
2. If the MAP signal circuit is open or shorted, repair it
as necessary.
Was the MAP signal circuit open or shorted?
ÐVerify repairGo to Step 12
5Replace the MAP sensor.
Is the action complete?
ÐVerify repairÐ
6Observe the TP angle reading on the Tech 2 while
slowly opening the throttle.
Does the TP 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 7
71. Disconnect the TP sensor.
2. Observe the TP sensor reading on the Tech 2.
Is the TP sensor reading near the specified value?
0 VGo to Step 8Go to Step 9
81. Connect a test light between the 5 volt reference ªAº
circuit and the TP sensor signal circuit at the TP
sensor harness connector.
2. Observe the TP sensor reading on the Tech 2.
Is the TP sensor reading at the specified value?
5 VGo to Step 11Go to Step 10
9Check the following items:
1. TP signal circuit for a short to voltage.
2. TP sensor ground circuit for high resistance
between the PCM and the TP sensor.
3. TP 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 12

6E±134
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0122 ±TP Sensor Circuit 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. With the throttle closed, observe the ªTP Sensorº
display on the Tech 2.
Is the ªTP Sensorº below the specified value?
0.22 VGo 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 ªDTCº info for DTC
P0122.
Does the Tech 2 indicate DTC P0122 failed?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the TP sensor electrical connector.
3. Jumper the 5 volt reference ªAº circuit and the TP
signal together at the TP sensor harness connector.
4. Ignition ªON.º
Observe the ªTP Sensorº display on the Tech 2.
Is the ªTP Sensorº at the specified value?
5 VGo to Step 10Go to Step 5
51. Disconnect jumper.
2. Connect a test light between B+ and the TP sensor
signal circuit at the TP sensor harness connector.
Observe the ªTP Sensorº display on the Tech 2.
Is the ªTP Sensorº at the specified value?
5 VGo to Step 6Go to Step 8
61. Ignition ªOFF.º
2. Disconnect the PCM and check the 5 volt reference
ªAº circuit for an open or short to ground.
3. If the 5 volt reference ªAº circuit is open or shorted to
ground, repair it as necessary.
Was the 5 volt reference ªAº circuit open or shorted to
ground?
ÐVerify repairGo to Step 7
7Check the 5 volt reference ªAº circuit for a poor
connection at the PCM and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 12
81. Ignition ªOFF.º
2. Disconnect the PCM, and check the TP signal
circuit for an open, short to ground, or short to the
sensor ground circuit.
3. If the TP sensor signal circuit is open or shorted to
ground, repair it as necessary.
Was the TP signal circuit open or shorted to ground?
ÐVerify repairGo to Step 9
9Check the TP sensor signal circuit for a poor
connection at the PCM and replace the terminal if
necessary.
Did the terminal require replacement?
ÐVerify repairGo to Step 12

6E±137 ENGINE DRIVEABILITY AND EMISSIONS
Disconnect the component while observing the TP
sensor display on the Tech 2. If the reading
changes drastically when this component isdisconnected, replace the component that affected
the reading.
DTC P0123 ± TP 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
21. Ignition ªON,º engine ªOFF.º
2. With the throttle closed, observe the ªTP Sensorº
display on the Tech 2.
Is the ªTP Sensorº above the specified value?
4.88 VGo 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 ªSpecific DTCº info for DTC
P0123.
Does the Tech 2 indicate DTC P0123 failed.
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Disconnect the TP sensor electrical connector.
2. Observe the ªTP Sensorº display on the Tech 2.
Is the ªTP Sensorº near the specified value?
0 VGo to Step 5Go to Step 6
5Probe the sensor ground circuit at the TP sensor
harness connector with a test light connected to B+.
Is the test light ªON?º
ÐGo to Step 7Go to Step 10
61. Ignition ªOFF,º disconnect the PCM.
2. Ignition ªON,º engine ªOFF.º
3. Check for a short to voltage on the TP sensor signal
circuit.
4. If the TP sensor signal circuit is shorted, repair it as
necessary.
Was the TP sensor signal circuit shorted?
ÐVerify repairGo to Step 12
71. Ignition ªON.º
2. Monitor the ªTP Sensorº Tech 2 display while
disconnecting each of the components that share
the 5 volt reference ªAº circuit (one at a time).
3. If the ªTP Sensorº Tech 2 display changes, replace
the component that caused the display to change
when disconnected.
Does disconnecting any of these components cause
the ªTP Sensorº display to change?
ÐVerify repairGo to Step 8
81. Ignition ªOFF,º disconnect the PCM.
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 ªAº circuit is shorted, repair it
as necessary.
Was the 5 volt reference ªAº circuit shorted?
ÐVerify repairGo to Step 9
9Check for poor electrical connections at the TP sensor
and replace terminals if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 11

6E±146
ENGINE DRIVEABILITY AND EMISSIONS
indicates a signal line shorted to ground or signal lines
shorted together. Disconnect the HO2S and connect
a test light between the HO2S ignition feed and heater
ground circuits. If the test light does not light for 2
seconds when the ignition is turned on, repair the open
ignition feed or sensor ground circuit as necessary. If
the test light lights and the HO2S signal and low circuits
are OK, replace the HO2S.

Intermittent test ± With the Ignition ªON,º monitor the
HO2S signal voltage while moving the wiring harness
and related connectors. If the fault is induced, the
HO2S signal voltage will change. This may help isolate
the location of the malfunction.Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
3. If the DTC P0134 test passes while the Failure
Records conditions are being duplicated, an
intermittent conditions is indicated.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
DTC P0134 ±HO2S Circuit Insufficient Activity Bank 1 Sensor 1

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Install Tech 2.
2. Run the engine at operating temperature.
3. Operate the engine above 1200 RPM for two
minutes.
Does Tech 2 indicate Bank 1 HO2S 1 voltage varying
outside the specified values?
400-500 mVGo to Step 3Go to Step 4
31. Ignition ªON,º engine ªOFF,º review and record Tech
2 Failure Records data and note parameters.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using Tech 2, monitor ªSpecific DTCº info for DTC
P0134 until the DTC P0134 test runs.
4. Note the test result.
Does Tech 2 indicate DTC P0134 failed this ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
4Check for a damaged harness.
Was a problem found?
ÐVerify repairGo to Step 5
5Check for poor Bank 1 HO2S 1 high and low circuit
terminal connections at the Bank 1 HO2S 1 harness
connector and replace terminal(s) if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 6
6Check for poor Bank 1 HO2S 1 high and low circuit
terminal connections at the PCM and replace terminals
if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 7
71. Ignition ªOFF.º
2. With the PCM disconnected, check continuity of the
Bank 1 HO2S 1 high circuit.
3. If the Bank 1 HO2S 1 high circuit measures over 5.0
ohms, repair open or poor connection as necessary.
Was a Bank 1 HO2S 1 high circuit problem found and
corrected?
ÐVerify repairGo to Step 8