engine coolant ISUZU TROOPER 1998 Service Manual PDF

6E±128
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 P0118 can be repeated only by duplicating
the Failure Records conditions, refer to the
ªTemperature vs. Resistance Valueº table. The
table may be used to test the ECT 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 ECT sensor. If the ECT sensor appears to be
OK, the fault is intermittent; refer to
Diagnostic Aids.
Engine Coolant Temperature Sensor

C
FOHMS
Temperature vs. Resistance Values
(approximate)
100212177
80176332
60140667
4511 31188
35951802
25772796
15594450
5417280
±52312300
±15521450
±30±2252700
±40±40100700
DTC P0118 ± ECT 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. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº below the specified value?
±39
C
(±38
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 the ªSpecific DTCº info for
DTC P0118.
Does the Tech 2 indicate DTC P0118 failed?
Ð
Refer to Test
Description
Refer to
Diagnostic
Aids
41. Disconnect the ECT sensor electrical connector.
2. Jumper the ECT signal circuit and the sensor
ground circuit together at the ECT sensor harness
connector.
3. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº at the specified value?
140
C
(284
F)
Go to Step 6Go to Step 5
51. Jumper the ECT signal circuit at the ECT sensor
harness connector to chassis ground.
2. Observe the ªEng Cool Tempº display on the Tech 2.
Is the ªEng Cool Tempº at the specified value?
140
C
(284
F)
Go to Step 7Go to Step 8
6Check for poor connections at the ECT sensor and
replace terminals if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 10

6E±139 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0131 HO2S Circuit Low Voltage Bank 1
Sensor 1
060RW236
Circuit Description
The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal high and signal low circuits. When
measured with a 10 megaohm digital voltmeter, this may
display as low as 350 mV. The oxygen sensor varies the
voltage within a range of about 1000 mV when the
exhaust is rich, down through about 10 mV when exhaust
is lean. The PCM constantly monitors the HO2S signal
during ªclosed loopº operation and compensates for a rich
or lean condition by decreasing or increasing injector
pulse width as necessary. If the Bank 1 HO2S 1 voltage
remains excessively low for an extended period of time,
DTC P0131 will be set.
Conditions for Setting the DTC

No related DTCs.

Vehicle is operating in ªclosed loop.º

Engine coolant temperature is above 60
C (140
F).

ªClosed loopº commanded air/fuel ratio is between
14.5 and 14.8.

Throttle angle is between 3% and 19%.

Bank 1 HO2S 1 signal voltage remains below 22 mV
during normal ªclosed loopº operation for a total of 77
seconds over a 90-second period of time.
Action Taken When the DTC Sets

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

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

ªOpen loopº fuel control will be in effect.
Conditions for Clearing the MIL/DTC

DTC P0131 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:

Heated oxygen sensor wiring ± The sensor pigtail may
be routed incorrectly and contacting the exhaust
system.

Poor PCM to engine block grounds.

Fuel pressure ± The system will go lean if pressure is
too low. The PCM can compensate for some
decrease. However, If fuel pressure is too low, a DTC
P0131 may be set. Refer to
Fuel System Diagnosis.

Lean injector(s) ± Perform ªInjector Balance Test.º

Vacuum leaks ± Check for disconnected or damaged
vacuum hoses and for vacuum leaks at the intake
manifold, throttle body, EGR system, and PCV system.

Exhaust leaks ± An exhaust leak may cause outside air
to be pulled into the exhaust gas stream past the

6E±142
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0132 HO2S Circuit High Voltage Bank 1
Sensor 1
060RW236
Circuit Description
The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal and low circuits. When measured
with a 10 megaohm digital voltmeter, this may display as
low as 320 mV. The oxygen sensor varies the voltage
within a range of about 1000 mV when exhaust is rich,
down through about 10 mV when exhaust is lean. The
PCM constantly monitors the HO2S signal during ªclosed
loopº operation and compensates for a rich or lean
condition by decreasing or increasing injector pulse width
as necessary. If the Bank 1 HO2S 1 voltage remains
excessively high for an extended period of time, DTC
P0132 will be set.
Conditions for Setting the DTC

No related DTCs.

Engine coolant temperature is above 60
C (140
F)

ªClosed loopº commanded air/fuel ratio is between
14.5 and 14.8.

Throttle angle is between 3% and 19%.

Bank 1 HO2S 1 signal voltage remains above 952 mV
during normal ªclosed loopº operation for a total of 77
seconds over a 90-second period.
OR

Bank 1 HO2S 1 signal voltage remains above 500 mV
during ªdeceleration fuel cutoff modeº operation for 3
seconds.
Action Taken When the DTC Sets

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

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

ªOpen loopº fuel control will be in effect.
Conditions for Clearing the MIL/DTC

DTC P0132 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check the following items:

Fuel pressure ± The system will go rich if pressure is
too high. The PCM can compensate for some
increase. However, if fuel pressure is too high, a DTC
P0132 may be set. Refer to
Fuel System Diagnosis.

Perform ªInjector Balance Testº ± Refer to
Fuel System
Diagnosis.

MAF sensor ±The system can go rich if MAF sensor
signal indicates an engine airflow measurement that is
not correct. Disconnect the MAF sensor to see it the
rich condition is corrected. If so, replace the MAF
sensor.

Check for a leak in the fuel pressure regulator
diaphragm by checking the vacuum line to the
regulator for the presence of fuel. There should be no
fuel in the vacuum line.

6E±148
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0151 HO2S Circuit Low Voltage Bank 2
Sensor 1
060RW190
Circuit Description
The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal high and signal low circuits. When
measured with a 10 megaohm digital voltmeter, this may
display as low as 320 mV. The oxygen sensor varies the
voltage within a range of about 1000 mV when the
exhaust is rich, down through about 10 mV when exhaust
is lean. The PCM constantly monitors the HO2S signal
during ªclosed loopº operation and compensates for a rich
or lean condition by decreasing or increasing injector
pulse width as necessary. If the Bank 2 HO2S 1 voltage
remains excessively low for an extended period of time,
DTC P0151 will be set.
Conditions for Setting the DTC

No related DTCs.

The engine is operating in ªclosed loop.º

Engine coolant temperature is above 60
C (140
F).

ªClosed loopº commanded air/fuel ratio is between
14.5 and 14.8.

Throttle angle is between 3% and 19%.

Bank 2 HO2S 1 signal voltage remains below 22 mV
during normal ªclosed loopº operation for a total of 77
seconds over a 90-second period of time.
Action Taken When the DTC Sets

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

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

ªOpen loopº fuel control will be in effect.
Conditions for Clearing the MIL/DTC

DTC P0151 can be cleared by using Tech 2 ªClear Infoº
function or by disconnecting the PCM battery feed.
Diagnostic Aids
Check for the following conditions:

Heated oxygen sensor wiring ± The sensor pigtail may
be mispositioned and contacting the exhaust system.

Poor PCM to engine block grounds.

Fuel pressure ± The system will go lean if pressure is
too low. The PCM can compensate for some
decrease. However, if fuel pressure is too low, a DTC
P0151 may be set. Refer to
Fuel System Diagnosis.

Lean injector(s) ± Perform ªInjector Balance Test.º

Vacuum leaks ± Check for disconnected or damaged
vacuum hoses and for vacuum leaks at the intake
manifold, throttle body, EGR system, and PCV system.

Exhaust leaks ± An exhaust leak may cause outside air
to be pulled into the exhaust gas stream past the
HO2S, causing the system to appear lean. Check for

6E±151 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0152 HO2S Circuit HIGH Voltage Bank 2
Sensor 1
060RW190
Circuit Description
The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal high and signal low circuits. When
measured with a 10 megaohm digital voltmeter, this may
display as low as 320 mV. The oxygen sensor varies the
voltage within a range of about 1000 mV when the
exhaust is rich, down through about 10 mV when exhaust
is lean. The PCM constantly monitors the HO2S signal
during ªclosed loopº operation and compensates for a rich
or lean condition by decreasing or increasing the injector
pulse width as necessary. If the Bank 2 HO2S 1 voltage
remains excessively high for an extended period of time,
DTC P0152 will be set.
Conditions for Setting the DTC

No related DTCs.

The engine is operating in ªclosed loop.º

The engine coolant temperature is above 60
C
(140
F).

ªClosed loopº commanded air/fuel ratio between 14.5
and 14.8.

Throttle angle between 3% and 19%.

Bank 2 HO2S 1 signal voltage remains above 952 mV
during normal ªclosed loopº operation for a total of 77
seconds over a 90-second period.
OR
Bank 2 HO2S 1 signal voltage remains above 500 mV
during deceleration fuel cutoff mode operation for up to
3 seconds.
Action Taken When the DTC Sets

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

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

ªOpen loopº fuel control will be in effect.
Conditions for Clearing the MIL/DTC

DTC P0152 can be cleared by using Tech 2 ªClear Infoº
function or by disconnecting the PCM battery feed.
Diagnostic Aids
Check for the following conditions:

Fuel pressure ± The system will go rich if pressure is
too high. The PCM can compensate for some
increase. However, if fuel pressure is too high, a DTC
P0152 may be set. Refer to
Fuel System Diagnosis.

Rich injector(s) ± Perform ªInjector Balance Test.º

Leaking injector ± Refer to
Fuel System Diagnosis.

Evaporative emissions (EVAP) system ± Check the
canister for fuel saturation. If the canister is full of fuel,
check EVAP control system components and hoses.
Refer to
Evaporative Emission (EVAP) Control
System.

6E±154
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0171 Fuel Trim System Lean Bank 1
D06RW030
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages. A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2. Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%. If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered. If an excessively lean condition is detected on
Bank 1, the PCM will set DTC P0171.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15% (automatic
transmission) or ±12% (manual transmission) and +20%.
The PCM monitors fuel trim under various enginespeed/load fuel trim cells before determining the status of
the fuel trim diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following: EGR DTCs, HO2S DTCs,
(response, transition, open, low volts, no activity), MAF
DTCs, TP sensor DTCs, MAP DTCs, IAT DTCs,
canister purge DTCs, EVAP DTCs, injector circuit
DTCs, or misfire DTCs.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

Barometric pressure is greater than 72.5 kPa.

6E±158
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0172 Fuel Trim System Rich Bank 1
D06RW030
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
heated oxygen sensors (HO2S) 1 and Bank 2 HO2S 1
signals and adjusts fuel delivery based upon the HO2S
signal voltages. A change made to fuel delivery will be
indicated by the long and short term fuel trim values which
can be monitored with a Tech 2. Ideal fuel trim values are
around 0%; if the HO2S signals are indicating a lean
condition the PCM will add fuel, resulting in fuel trim
values above 0%. If a rich condition is detected, the fuel
trim values will be below 0%, indicating that the PCM is
reducing the amount of fuel delivered. If an excessively
rich condition is detected on Bank 1, the PCM will set DTC
P0172.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15% (automatic
transmission) or ±12 (manual transmission) and +20%.The PCM's maximum authority to control short term fuel
trim allows a range between ±11% and +20%. The PCM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following was set: EGR DTCs, HO2S
DTCs, (response, transition, open, low volts, no
activity), MAF DTCs, TPS DTCs, MAP DTCs, IAT
DTCs, canister purge DTCs, EVAP DTCs, injector
circuit DTCs, or misfire DTCs.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

6E±162
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0174 Fuel Trim System Lean Bank 2
D06RW031
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages. A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2. Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%. If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered. If an excessively lean condition is detected on
Bank 2, the PCM will set DTC P0174.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15%(automatic
transmission) or ±12%(manual transmission) and +20%.
The PCM monitors fuel trim under various enginespeed/load fuel trim cells before determining the status of
the fuel trim diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following DTCs are set: idle system, EGR,
HO2S, (response, transition, open, low volts, no
activity), MAF, TP sensor, MAP, IAT, canister purge,
EVAP, injector circuit, or misfire.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

Barometric pressure is greater than 72.5 kPa.

Mass air flow is between 2 g/second and 200 g/second.

6E±166
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0175 Fuel Trim System Rich Bank 2
D06RW031
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loop,º
the powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages. A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2. Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%. If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered. If an excessively rich condition is detected on
Bank 2, the PCM will set DTC P0175.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15%(automatic
transmission) or ±12%(manual transmission) and +20%.
The PCM's maximum authority to control short term fueltrim allows a range between ±11% and +20%. The PCM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.
Conditions for Setting the DTC

No Tech 2 test is being run.

None of the following DTCs are set: idle system, EGR,
HO2S, (response, transition, open, low volts, no
activity), MAF, TPS, MAP, IAT, canister purge, EVAP,
injector circuit, or misfire.

Engine coolant temperature is between 25
C (77
F)
and 100
C (212
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

6E±234
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0502 VSS Circuit Low Input
D06RW019
Circuit Description
The vehicle speed sensor has a magnet rotated by the
transmission output shaft. Attached to the sensor is a hall
effect circuit the interacts with the magnetic field treated
by the rotating magnet. A 12-volt operating supply for the
speed sensor hall circuit is supplied from the meter fuse.
The VSS pulses to ground the 9-volt signal sent from the
powertrain control module (PCM) on the reference circuit.
The PCM interprets vehicle speed by the number of
pulses to ground per second on the reference circuit.
Conditions for Setting the DTC

Engine is running.

Engine coolant temperature is above 60
C (140
F).

Engine speed is between 1800 RPM and 2500 RPM.

Throttle angle is between 10% and 40%.

Engine load is greater than 50 kPa.

MAP sensor indicates greater than 50 kPa manifold
pressure.

PCM detects no VSS signal for 12.5 seconds over a
period of 25 seconds.
Action Taken When the DTC Sets

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

The PCM 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 P0502 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
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
connects to the engine harness. Power and ground
are applied by jumpers to the VSS through the
connectors which are located just in front of the air
cleaner assembly. The VSS signal is monitored
with a DVM as the rear driveshaft turns. The
wheels can be turned to rotate the driveshaft, or in
2-wheels-drive vehicles the driveshaft can be turned
directly.
12. The speedometer-to-PCM VSS signal wire is
spliced to a wire leading to the cruise control
module. If a short to ground or voltage is indicated
between the PCM and speedometer, it could be on
the cruise control circuit if the vehicle is equipped
with cruise control.