1998 ISUZU TROOPER check engine

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±72
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0122 (Flash DTC 21)
AP Sensor Low Voltage
060RW134
Circuit Description
The accelerator position (AP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.
The AP signal is used by the Engine Control Module ECM
for fuel volume control and many of the ECM-controlled
outputs.
Action Taken When the DTC Sets

The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P0122 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:

Poor connection at ECM ± Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.

Damaged harness ± Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
throttle position display on the Tech 2 while moving
connectors and wiring harnesses related to the TP
sensor. A change in the display will indicate the
location of the fault.
If DTC P0122 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
DTC P0122 ±AP 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
2Check the AP sensor signal circuit.
Was the AP sensor signal circuit open or darmage?
Ð
Replace the
APS circuit
Go to Step 3

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±75 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0123 (Flash DTC 21)
AP Sensor High Voltage
060RW134
Circuit Description
The accelerator position (AP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.
The TP signal is one of the most important inputs used by
the Engine Control Module ECM for fuel volume control
and many of the ECM-controlled outputs.
Action Taken When the DTC Sets

The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P0123 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:

Poor connection at ECM ± Inspect harness connectors
for backed-out terminals, improper mating, brokenlocks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.

Damaged harness ± Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
AP sensor display on the Tech 2 while moving
connectors and wiring harnesses related to the TP
sensor. A change in the display will indicate the
location of the fault.

Faulty AP sensor ± With the ignition key ªON,º engine
ªOFF,º observe the AP sensor display on the Tech 2
while slowly depressing the accelerator to wide open
throttle. If a voltage over 4.88 volts is seen at any point
in normal accelerator travel, replace the AP sensor.
If DTC P0123 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
Test Description
Number (s) below refer to the step number(s) on the
Diagnostic Chart.
8. Components that share the AP sensor 5 volt reference
ªAº circuit include the following device:

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±77 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0123 ± AP Sensor High Voltage

 
StepNo Ye s Value(s) Action
111. Ignition ªOFF.º
2. Disconnect the ECM, and check for an open sensor
ground circuit to the AP sensor.
3. If a problem is found, repair it as necessary.
Was the sensor ground circuit to the AP sensor open?
ÐVerify repairGo to Step 13
12Replace the AP sensor.
Is the action complete?
ÐVerify repairÐ
13Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairÐ

6E±78
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0182 (Flash DTC 15)
FT Sensor Low Voltage
060RW129
Circuit Description
The fuel temperature (FT) sensor is a thermistor mounted
on a coolant crossover pipe at the rear of the engine. The
Engine Control Module ECM applies a voltage (about 5
volts) through a pull-up resistor to the FT signal circuit.
When the fuel is cold, the sensor (thermistor) resistance
is high, therefore the ECM will measure a high signal
voltage. As the fuel warms, the sensor resistance
becomes lower, and the FT signal voltage measured at
the ECM drops.
Action Taken When the DTC Sets

The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P0182 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:

Poor connection at ECM ± Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.

Damaged harness ± Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
FT display on the Tech 2 while moving connectors and
wiring harnesses related to the FT sensor. A change
in the FT display will indicate the location of the fault.
If DTC P0182 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
If it is determined that the DTC occurs intermittently.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Verifies that the fault is present.

6E±79 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0182 ± FT 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 ªFuel Tempº display on the Tech 2.
Is the ªFuel 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 P0182.
Does the Tech 2 indicate DTC P0182 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Disconnect the FT sensor electrical connector.
2. Observe the ªFuel Tempº display on the Tech 2.
Is the ªFuel 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 FT signal circuit
for a short to ground or a short to the sensor ground
circuit.
3. If the FT signal circuit is shorted. repair it as
necessary.
Was the FT signal circuit shorted to ground?
ÐVerify repairGo to Step 7
6Replace the FT 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