1998 ISUZU TROOPER check engine

6E±88
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1194 (Flash DTC 61)
Rail Pressure System Low Voltage
060RW134
Circuit Description
The rail pressure (RP) sensor responds to changes in oil
rail pressure.
The ECM monitors the RP signals for voltages outside the
normal range of the RP sensor. If the ECM detects a RP
signal voltage that is excessively low, DTC P1194 will be
set.
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 P1194 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:

Check for intermittent codes.

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
MAP display on the Tech 2 while moving connectors
and wiring harnesses related to the sensor. A change
in the display will indicate the location of the fault.
If DTC P1194 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,
performing the DTC P1194 Diagnostic Chart may isolate
the cause of the fault.

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±90
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1195 (Flash DTC 61)
Rail Pressure System High Voltage
060RW134
Circuit Description
The rail pressure (RP) sensor responds to changes in oil
rail pressure.
The ECM monitors the RP signals for voltages outside the
normal range of the RP sensor. If the ECM detects a RP
signal voltage that is excessively low, DTC P1195 will be
set.
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 P1195 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:

Check for intermittent codes.

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
MAP display on the Tech 2 while moving connectors
and wiring harnesses related to the sensor. A change
in the display will indicate the location of the fault.
If DTC P1195 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,
performing the DTC P1195 Diagnostic Chart may isolate
the cause of the fault.

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±93 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Circuit Description
The rail pressure control valve (RPCV) is built in the high
pressure oil circuit.
RPCV is an important device which is used to control oil
pressure in the HEUI system.
The circuit receives current through Engine 15A fuse from
the battery, current flowing in the order of RPCV.
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 P1196 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
Rail Pressure Control display on the Tech 2 while
moving connectors and wiring harnesses related to the
Rail Pressure Control. A change in the Rail Pressure
Control display will indicate the location of the fault.
If DTC P1196 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.
DTC P1196 ± RP System High Warning

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. Observe the ªRail Pressure Controlº display on the
Tech 2.
Is the action correct?
ÐGo to Step 4Go to Step 3
3Replace the RPCV.
Is the action complete?
ÐVerify repairGo to Step 4
41. 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 ª DTCº info for DTC P1196.
Does the Tech 2 indicate DTC P1196 failed this
ignition?
ÐGo to Step 5Ð
51. Check the 2 way valve.
2. Observe the ªRP Controlº display on the Tech 2.
Is the action correct?
ÐGo to Step 4Go to Step 6
6Replace the 2 way valve.
Is the action complete?
ÐVerify repairÐ

6E±94
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0197 (Flash DTC 16)
Oil Temp Sensor Low Voltage
060RW129
Circuit Description
The engine oil temperature (OT) sensor is a thermistor
mounted in the oil rail. The Engine Control Module ECM
applies a voltage (about 5 volts) through a pull-up resistor
to the ECT signal circuit. When the engine oil is cold, the
sensor (thermistor) resistance is high, therefore the ECM
will measure a high signal voltage. As the engine oil
warms, the sensor resistance becomes lower, and the OT
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 P0197 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
OT display on the Tech 2 while moving connectors and
wiring harnesses related to the OT sensor. A change
in the OT display will indicate the location of the fault.
If DTC P0197 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.

6E±95 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 P0197 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 OT 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 OT sensor. If the OT sensor appears to be OK,
the fault is intermittent; refer to
Diagnostic Aids.
Engine Oil Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
80176332
25772796
15594450
DTC P0197 ± OT 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 Oil Tempº display on the Tech 2.
Is the ªEng Oil 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 P0197.
Does the Tech 2 indicate DTC P0197 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Disconnect the OT sensor electrical connector.
2. Observe the ªEng Oil Tempº display on the Tech 2.
Is the ªEng Oil 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 OT signal circuit
for a short to ground or a short to the sensor ground
circuit.
3. If the OT signal circuit is shorted. repair it as
necessary.
Was the OT signal circuit shorted to ground?
ÐVerify repairGo to Step 7
6Replace the OT 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±96
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0198 (Flash DTC 16)
Oil Temp Sensor High Voltage
060RW129
Circuit Description
The engine oil temperature (OT) sensor is a thermistor
mounted in the oil rail. The Engine Control Module ECM
applies a voltage (about 5 volts) through a pull-up resistor
to the ECT signal circuit. When the engine oil is cold, the
sensor (thermistor) resistance is high, therefore the ECM
will measure a high signal voltage. As the engine oil
warms, the sensor resistance becomes lower, and the OT
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 P0198 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
OT display on the Tech 2 while moving connectors and
wiring harnesses related to the OT sensor. A change
in the OT display will indicate the location of the fault.
If DTC P0198 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.