Intake sensor ISUZU TROOPER 1998 Service Repair Manual

6E±60
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0112 (Flash DTC 23)
IAT Sensor Circuit Low Voltage
060RW129
Circuit Description
The Intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine. The Engine Control Module ECM applies 5 volts
through a pull-up resistor to the IAT sensor. When the
intake air is cold, the sensor resistance is high and the
ECM will monitor a high signal voltage on the IAT signal
circuit. If the intake air is warm, the sensor resistance is
lower, causing the ECM to monitor a lower voltage. DTC
P0112 will set when the ECM detects an excessively low
signal voltage on the Intake air temperature sensor signal
circuit.
Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

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 P0112 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
IAT display on the Tech 2 while moving connectors and
wiring harnesses related to the IAT sensor. A change
in the IAT display will indicate the location of the fault.
If DTC P0112 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E±61 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 P0112 can be repeated only by duplicating
the Failure Records condition, refer to the
Temperature vs. Resistance Value table. The table
may be used to test the IAT sensor at various
temperatures to evaluate the possibility of a
ªshiftedº sensor that may be stored above or below
a certain temperature. If this is the case, replace
the IAT sensor. If the IAT sensor appears to be OK,
the fault is intermittent; refer to
Diagnostic Aids.
Intake Air Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
25772796
15594450
5417280
DTC P0112 ± IAT 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. Using a Tech 2, monitor the intake air temperature
(IAT).
Is the intake air temperature greater than the specified
value?
148
C
(283
F)
Go to Step 4Go to Step 3
31. Ignition ªON,º engine ªOFF.º Review and record
Tech 2 Failure Records data.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor the ª DTCº info for DTC
P0112.
Does the Tech 2 indicate DTC P0112 failed this
ignition?
Ð
Refer to Test
Description
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the IAT sensor electrical connector.
3. Ignition ªON.º
4. Observe the manifold air temperature on the Tech 2.
Is the manifold air temperature below the specified
value?
±38
C
(±36
F)
Go to Step 6Go to Step 5
51. Ignition ªOFF.º
2. Disconnect the ECM electrical connectors.
3. Check the IAT sensor signal circuit for a short to
ground.
Is the IAT sensor signal circuit shorted to ground?
ÐVerify repairGo to Step 7
6Replace the IAT 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±62
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0113 (Flash DTC 23)
IAT Sensor Circuit High Voltage
060RW129
Circuit Description
The intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine. The Engine Control Module ECM applies 5 volts
through a pull-up resistor to the IAT sensor. When the
intake air is cold, the sensor resistance is high and the
ECM will monitor a high signal voltage on the IAT signal
circuit. If the intake air is warm, the sensor resistance is
lower causing the ECM to monitor a lower voltage. DTC
P0113 will set when the ECM detects an excessively high
signal voltage on the intake air temperature sensor signal
circuit.
Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

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 P0113 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
IAT display on the Tech 2 while moving connectors and
wiring harnesses related to the IAT sensor. A change
in the IAT display will indicate the location of the fault.
If DTC P0113 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E±63 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 P0113 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 MAT sensor at various
temperatures to evaluate the possibility of a
ªshiftedº sensor that may be open above or below a
certain temperature. If this is the case, replace the
MAT sensor. If the MAT sensor appears to be OK,
the fault is intermittent; refer to
Diagnostic Aids.
Manifold Air Temperature Sensor

C
FOhms
Temperature vs. Resistance Values
(approximate)
25772796
15594450
5417280
DTC P0113 ±IAT 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
2Ignition ªON,º engine ªOFF.º Observe the ªIntake Air
Tempº display on the Tech 2.
Is the ªIntake Air Tempº below the specified value?
±38
C
(±36
F)
Go to Step 4Go to Step 3
31. Ignition ªON,º engine ªOFF.º
2. Review and record Tech 2 Failure Records data
parameters.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor ª DTCº info for DTC P0113.
Does the Tech 2 indicate DTC P0113 failed?
Ð
Refer to Test
Description
Refer to
Diagnostic
Aids
41. Ignition ªOFF.º
2. Disconnect the IAT sensor electrical connector.
3. Jumper the IAT signal circuit and the sensor ground
circuit together at the IAT sensor harness
connector.
4. Ignition ªON.º
5. Observe the ªIntake Air Tempº display on the Tech
2.
Is the ªIntake Air Tempº at the specified value?
140
C
(284
F)
Go to Step 6Go to Step 5
51. Jumper the IAT signal circuit at the IAT sensor
harness connector to chassis ground.
2. Observe the ªIntake Air Tempº display on the Tech
2.
Is the ªIntake Air Tempº at the specified value?
140
C
(284
F)
Go to Step 7Go to Step 8
6Check for poor connections at the IAT sensor and
replace terminals if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 10
71. Ignition ªOFF.º
2. Disconnect the ECM, and check the IAT sensor
ground circuit for an open.
3. If the IAT sensor ground circuit is open, repair it as
necessary.
Was the IAT sensor ground circuit open?
ÐVerify repairGo to Step 9

6E±92
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1196 (Flash DTC 62)
Rail Pressure System High Warning
060RW178
Legend
(1) ECM
(2) Meter Panel
(3) Battery
(4) Oil Temp Sensor
(5) Rail Pressure Sensor
(6) Glow Relay
(7) Oil Rail
(8) Tech±2
(9) A/C Comp Relay
(10) RPCV
(11) Intake Air Temp Sensor
(12) Engine Coolant Temp Sensor
(13) MAP Sensor
(14) EGR Valve
(15) EGR Pressure Sensor(16) High Pressure Oil Pump
(17) Fuel Pump
(18) VSV
(19) EXH Throttle VSV1
(20) EXH Throttle VSV2
(21) EVRV
(22) Engine Harness Connector
(23) QWS Relay
(24) AP Sensor
(25) T.O.D
(26) ECT
(27) OBD
(28) TDC
(29) Injector
(30) Edge Filter

6E±130
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1403 (Flash DTC 32)
EGR EVRV Fault
060RW135
Circuit Description
EGR EVRV Circuit has a common power source in
parallel with EGR, VSV, RPCV, and Intake Throttle Motor.
This may cause multiple DTCs. On such occasion, refer
to ªMultiple ECM Information sensor DTCs Setº.
Diagnostic Aids
Check for the following conditions:

Poor connection or damaged EVRV ± Inspect the
wiring harness for damage.

Ensure EVRV is correctly mounted. See
On-Vehicle
Service.
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.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart
3. A malfunctioning MAP sensor can set an EGR DTC.
The MAP sensor could send a constant signal which
is not low enough to set a low MAP DTC. The
constant signal from the MAP sensor also may not
be high enough to set a high MAP DTC. This step
verifies that the MAP sensor is responding.

6E±136
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1405 (Flash DTC 37)
EGR EVRV Circuit Open/Short
060RW135
Circuit Description
EGR EVRV Circuit has a common power source in
parallel with EGR, VSV, RPCV, and Intake Throttle Motor.
This may cause multiple DTCs. On such occasion, refer
to ªMultiple ECM Information Sensor DTCs Setº.
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 P1405 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the ECM battery
feed.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside the
insulation. Check for:

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

Damaged harness ± Inspect the wiring harness for
damage.

6E±144
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1485 (Flash DTC 74)
ITP (Intake Thorottle Position) Sensor Low Voltage
060RW134
Circuit Description
The intake throttle position (ITP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.
Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

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 P1485 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 ITP sensor. A change in the display will
indicate the location of the fault.
If DTC P1485 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 P1485 ±ITP 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. With the throttle closed by the hand, observe the
ªITP Sensorº display on the Tech 2.
Is the ªITP Sensorº below the specified value?
0.22 VGo to Step 4Go to Step 3

6E±145 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P1485 ±ITP Sensor Low Voltage

 
StepNo Ye s Value(s) Action
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
P1485.
Does the Tech 2 indicate DTC P1485 failed?
ÐGo to Step 4
Refer to
Diagnostic
Aids
4Check the ITP 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 5
51. 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 ªSpecific DTCº info for
DTC P1485.
Dose the Tech 2 indicate DTC P1485 failed?
ÐGo to Step 6
Refer to
Diagnostic
Aids
6Replace the intake throttle.
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±146
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1486 (Flash DTC 74)
ITP (Intake Throttle Position) Sensor High Voltage
060RW134
Circuit Description
The intake throttle position (ITP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle.
Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

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 P1486 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
ITP 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 TP sensor ± With the ignition key ªON,º engine
ªOFF,º observe the TP sensor display on the Tech 2
while slowly depressing the accelerator to wide open
throttle.
If DTC P1486 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.