display ISUZU AXIOM 2002 Service Manual PDF

6E±170
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

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

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.

An intermittent TP sensor output will cause the system
to go rich due to a false indication of the engine
acceleration.

Shorted Heated Oxygen Sensor (HO2S) ±If the HO2S
is internally shorted, the HO2S voltage displayed on
the Tech 2 will be over 1 volt. Try disconnecting the
affected HO2S with the key ªONº, engine ªOFFº. If the
displayed HO2S voltage changes from over 1000 mV
to around 450 mV, replace the HO2S. Silicon
contamination of the HO2S can also cause a high
HO2S voltage to be indicated. This condition is
indicated by a powdery deposit on the portion of the
HO2S exposed to the exhaust stream. If
contamination is noticed, replace the affected HO2S.

Open HO2S Signal Circuit or Faulty HO2S±A poor
connection or open in the HO2S signal circuit cancause the DTC to set during deceleration fuel mode.
An HO2S which is faulty and not allowing a full voltage
swing between the rich and lean thresholds can also
cause this condition. Operate the vehicle by
monitoring the HO2S voltage with a Tech 2. If the
HO2S voltage is limited within a range between 300
mV to 600 mV, check the HO2S signal circuit wiring
and associated terminal conditions.

If none of the above conditions are present, replace the
affected HO2S.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
3. DTC P0132 failing during ªdeceleration fuel cutoff
modeº operation may indicate a condition described
in the ªDiagnostic Aidsº above. If the DTC P0132
test passes while the Failure Records conditions are
being duplicated, an intermittent condition 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 P0132 ± HO2S Circuit High Voltage 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 the Tech 2.
2. Run the engine at operating temperature.
3. Operate the vehicle within parameters specified
under ªConditions for Setting the DTCº included in
Diagnostic Support.
4. Using a Tech 2, monitor Bank 1 HO2S 1 voltage.
Does the Bank 1 HO2S 1 voltage remain above the
specified value?
952 mV (500
mV in
deceleration
fuel cutoff
mode)
Go to Step 4Go to Step 3
31. Ignition ªONº, review and record Tech 2 Failure
Records data.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor ªDTCº info for DTC P0132
until the DTC P0132 test runs.
4. Note the test result.
Does the Tech 2 indicate DTC P0132 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Ignition ªOFFº.
2. Disconnect Bank 1 HO2S 1.
3. Ignition ªONº.
4. At HO2S Bank 1 Sensor 1 connector (PCM side)
use a DVM to measure voltages at the high and low
signal terminals.
Are the voltages in the specified range?
3-4 VGo to Step 5Go to Step 6

6E±173
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check for the following conditions:

Poor connection at PCM ± 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
Bank 1 HO2S 1 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 P0133 cannot be duplicated, 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.
2. Verifies that the fault is currently present.
3. HO2S transition time, ratio mean volts and switching
DTCs set for multiple sensors indicate probable
contamination. Before replacing the sensors,
isolate and correct the source of the contamination
to avoid damaging the replacement sensors.

6E±176
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P0134 HO2S Circuit Insufficient Activity Bank 1 Sensor 1
060R200054
Circuit Description

The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) high 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 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 at or near the 450 mV
bias for an extended period of time, DTC P0134 will be
set, indicating an open sensor signal or sensor low
circuit.

Heated oxygen sensors are used to minimize the
amount of time required for ªclosed loopº fuel control
operation and to allow accurate catalyst monitoring.
The oxygen sensor heater greatly decreases the
amount of time required for fuel control sensors Bank
1 HO2S 1 and Bank 2 HO2S 1 to become active.

Oxygen sensor heaters are required by post-catalyst
monitor sensors to maintain a sufficiently high
temperature for accurate exhaust oxygen content
readings further from the engine.
Conditions for Setting the DTC

No related DTCs.

Battery voltage is above 10 volts.
The engine has been running for over 5 seconds.

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

Oxygen sensor heater has been determined to be
functioning properly.

Bank 1 HO2S 1 signal voltage remains between
400 mV and 500 mV for a total of 77 seconds over a
90-second period of time.
Action Take When the DTC Sets

The PCM will ON the MIL after second trip with
detected fault.

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

The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

A history DTC P0134 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0134 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.

6E±177
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check for the following conditions:

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

Faulty HO2S heater or heater circuit ± With the ignition
ªONº, engine ªOFFº, after a cool down period, the
HO2S 1 voltage displayed on the Tech 2 is normally
455-460 mV. A reading over 1000 mV indicates a
signal line shorted to voltage. A reading under 5 mV
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 ªONº, 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 the Tech 2.
2. Run the engine at operating temperature.
3. Operate the engine above 1200 RPM for two
minutes.
Does the Tech 2 indicate Bank 1 HO2S 1 voltage
varying outside the specified values?
400-500 mVGo to Step 3Go to Step 4
31. Ignition ªONº, engine ªOFFº, review and record
Tech 2 Failure Records data and note parameters.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor ªDTCº info for DTC P0134
until the DTC P0134 test runs.
4. Note the test result.
Does the 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

6E±180
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check for the following conditions:

Poor connection at PCM ± 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
ECT 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.
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.2. The HO2S should be allowed to cool before
performing this test. If the HO2S heater is
functioning, the signal voltage will gradually increase
or decrease as the sensor element warms. If the
heater is not functioning, the HO2S signal will
remain near the 450 mV bias voltage.
4. Ensures that the ignition feed circuit to the HO2S is
not open or shorted. The test light should be
connected to a good chassis ground, in case the
HO2S low or HO2S heater ground circuit is faulty.
5. Checks the HO2S heater ground circuit.
6. Checks or an open or shorted HO2S heater element.
10.An open HO2S signal or low circuit can cause the
HO2S heater to appear faulty. Check these circuits
before replacing the sensor.
DTC P0135 ± HO2S Heater Circuit 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
2NOTE: If the engine has just been operating ,allow the
engine to cool for at least 15 minutes before
proceeding.
1. Remove the fuel pump relay.
2. Connect a fused jumper at the fuel pump relay
socket, between the battery positive at the relay and
the relay wire that leads to the fuel pump and HO2S
fuses.
3. Ignition ªOFFº.
4. Install a Tech 2.
5. Ignition ªONº, engine ªOFFº.
6. Monitor the Bank 1 HO2S 1 voltage for several
minutes.
Did the HO2S voltage go from bias voltage to above or
below the specified values?
Above
650 mV or
below
250 mV
Refer to
Diagnostic
Aids
Go to Step 3
3Inspect the fuse for the Bank 1 HO2S 1 ignition feed.
Is the fuse open?
ÐGo to Step 15Go to Step 4
41. Ignition ªOFFº.
2. Raise the vehicle.
3. Disconnect the Bank 1 HO2S 1 electrical connector.
4. Using a test light connected to a good ground (do
not use Bank 1 HO2S 1 heater ground or Bank 1
HO2S 1 low), probe the ignition feed circuit at the
Bank 1 HO2S 1 electrical connector (PCM harness
side).
Does the test light illuminate?
ÐGo to Step 5Go to Step 7
5Connect the test light between the Bank 1 HO2S 1
ignition feed and the Bank 1 HO2S 1 heater ground.
Does the test light illuminate?
ÐGo to Step 6Go to Step 8

6E±182
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2
060R200054
Circuit Description
The powertrain control module (PCM) supplies bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal high and signal low circuits. When
measured with a 10 megaohm impedance digital
voltmeter, this may display as low as 350 mV. The
oxygen sensor varies the voltage within a range of about
1000 mV when exhaust is rich, down through about
10 mV when the 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 2 signal voltage remains
excessively low for an extended period of time, DTC
P0137 will be set.
Conditions for Setting the DTC

No related DTCs.

Engine is operating in ªclosed loopº.

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 2 signal voltage remains below 22 mV
during normal ªclosed loopº operation for a total of 106
seconds over a 125-second period of time.
OR
Bank 1 HO2S 2 signal voltage remains below 400 mV
during power enrichment mode fuel control operation
for up to 5 seconds.
Action Taken When the DTC Sets

The PCM will ON the MIL after second trip with
detected fault.

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

The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

A history DTC P0137 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0137 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 mispositioned and contacting the exhaust system.

Poor PCM to engine grounds.

Fuel pressure ± A condition which causes a lean
exhaust can cause DTC P0137 to set. The system will
go lean if pressure is too low. The PCM can

6E±185
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P0138 HO2S Circuit High Voltage Bank 1 Sensor 2
060R200054
Circuit Description
The powertrain control module (PCM) supplies 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 exhaust is
rich, down through about 10 mV when the 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 2 voltage
remains excessively high for an extended period of time,
DTC P0138 will be set.
Conditions for Setting the DTC

No related DTCs.

Engine is operating in ªclosed loopº.

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

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

Throttle angle is between 3% and 19%.

Bank 1 HO2S 2 signal voltage remains above 952 mV
during normal ªclosed loopº operation for a total of 106
seconds over a 125-second period of time.
OR
Bank 1 HO2S 2 signal voltage remains above 500 mV
during deceleration fuel cut±off mode operation for up
to 3 seconds.
Action Taken When the DTC Sets

The PCM will ON the MIL after second trip with
detected fault.

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

The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

A history DTC P0138 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0138 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:

Fuel pressure ± An excessively rich fuel mixture can
cause a DTC P0138 to be set. Refer to
Fuel System
Diagnosis.

Rich injector(s) ± Perform ªInjector Balance Testº.

Leaking injector ± Refer to
Fuel System Diagnosis.

6E±186
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

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

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

Check for a leak in 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.

TP sensor ± An intermittent TP sensor output will
cause the system to go rich, due to a false indication
of the engine accelerating.

Shorted Heated Oxygen Sensor (HO2S) ± If the HO2S
is internally shorted the HO2S voltage displayed on the
Tech 2 will be over 1 volt. Try disconnecting the
affected HO2S with the key ªONº, engine ªOFFº. If the
displayed HO2S voltage changes from over 1000 mV
to around 450 mV, replace the HO2S. Silicon
contamination of the HO2S can also cause a high
HO2S voltage to be indicated. This condition is
indicated by a powdery deposit on the portion of the
HO2S exposed to the exhaust stream. If
contamination is noticed, replace the affected HO2S.
Open HO2S Signal Circuit of Faulty HO2S ± A poor
connection or open in the HO2S signal circuit can
cause the DTC to set during deceleration fuel mode.
An HO2S which is faulty and not allowing a full voltage
swing between the rich and lean thresholds can also
cause this condition. Operate the vehicle while
monitoring the HO2S voltage with a Tech 2. If the
HO2S voltage is limited within a range between
300 mV to 600 mV, check the HO2S signal and wiring
and associated terminal connections.

If none of the above conditions are present, replace the
affected HO2S.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
3. DTC P0138 being set during deceleration fuel mode
operation may indicate a condition described in the
ªDiagnostic Aidsº above. If the DTC P0138 test
passes while the Failure Records conditions are
being duplicated, an intermittent condition 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 P0138 ± HO2S Circuit High Voltage Bank 1 Sensor 2

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Install the Tech 2.
2. Run the engine at operating temperature.
3. Operate the vehicle within the parameters specified
under ªConditions for Setting the DTCº criteria
included in Diagnostic Support.
4. Using a Tech 2, monitor Bank 1 HO2S 2 voltage.
Does the Bank 1 HO2S voltage remain above the
specified value?
952 mV
(500 mV in
deceleration
fuel cutoff
mode)
Go to Step 4Go to Step 3
31. Ignition ªONº, review and record Tech 2 Failure
Records data.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor ªDTCº info for DTC P0138
until the DTC P0138 test runs.
4. Note the test result.
Does the Tech 2 indicate DTC P0138 failed this
ignition?
ÐGo to Step 4
Refer to
Diagnostic
Aids
41. Ignition ªOFFº.
2. Disconnect Bank 1 HO2S 1.
3. Ignition ªONº.
4. At the HO2S Bank 1 Sensor 2 connector (PCM
side), use a DVM to measure voltages at the high
and low signal terminals.
Are the voltages above the specified range?
3-4 VGo to Step 5Go to Step 6

6E±189
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check for the following conditions:

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

Faulty HO2S heater or heater circuit±With the
ignitionªONº, engine ªOFFº, the HO2S voltage
displayed on a Tech 2 should gradually drop to below
250 mV. If not, disconnect the HO2S and connect a
test light between the HO2S ignition feed and heater
ground circuits. If the test light does not light, 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 ªONº, 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 P0140 test passes while the Failure
Records conditions are being duplicated, an
intermittent condition 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 P0140 ± HO2S Circuit Insufficient Activity BANK 1 SENSOR 2

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Install the Tech 2.
2. Run the engine at operating temperature.
3. Operate the engine above 1200 RPM for two
minutes.
Does the Tech 2 indicate Bank 1 HO2S 2 voltage
varying outside the specified values?
425-475 mVGo to Step 3Go to Step 4
31. Ignition ªONº, engine ªOFFº, review and record
Tech 2 Failure Records data and note parameters.
2. Operate the vehicle within Failure Records
conditions as noted.
3. Using a Tech 2, monitor ªDTCº info for DTC P0140
until the DTC P0140 test runs.
4. Note the test result.
Does the Tech 2 indicate DTC P0140 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 2 high and low circuit
terminal connections at the Bank 1 HO2S 2 harness
connector and replace terminal(s) if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 6
6Check for poor Bank 1 HO2S 2 high and low circuit
terminal connections at the PCM and replace
terminal(s) if necessary.
Did any terminals require replacement?
ÐVerify repairGo to Step 7
71. Ignition ªOFFº.
2. With the PCM disconnected, check continuity of the
Bank 1 HO2S 2 high circuit.
3. If the Bank 1 HO2S 2 high circuit measures over 5.0
ohms, repair open or poor connection as necessary.
Was a Bank 1 HO2S 2 high circuit problem found and
corrected?
ÐVerify repairGo to Step 8

6E±192
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Poor connection at PCM ± 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
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.
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.2. The HO2S should be allowed to cool before
performing this test. If the HO2S heater is
functioning, the signal voltage will gradually increase
or decrease as the sensor element warms. If the
heater is not functioning, the HO2S signal will
remain near the 450 mV bias voltage.
4. This ensures that the ignition feed circuit to the
HO2S is not open or shorted. The test light should
be connected to a good chassis ground, in case the
HO2S low or HO2S heater ground circuit is faulty.
5. This checks the HO2S heater ground circuit.
6. This checks for an open or shorted HO2S heater
element.
11.An open HO2S signal or low circuit can cause the
HO2S heater to appear faulty. Check these circuits
before replacing the sensor.
DTC P0141 ± HO2S Heater Circuit Bank 1 Sensor 2

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2NOTE: If the engine has just been operating, allow the
engine to cool for at least 15 minutes before
proceeding.
1. Remove the fuel pump relay.
2. Connect a fused jumper at the fuel pump relay
socket, between the battery positive at the relay and
the relay wire that leads to the fuel pump and HO2S
fuses.
3. Ignition ªOFFº.
4. Install a Tech 2.
5. Ignition ªONº, engine ªOFFº.
6. Monitor the Bank 1 HO2S 2 voltage for several
minutes.
Did the HO2S voltage go from bias voltage to above or
below the specified values?
Above
650 mV or
below
250 mV
Refer to
Diagnostic
Aids
Go to Step 3
3Inspect the fuse for Bank 1 HO2S 2 ignition feed.
Is the fuse open?
ÐGo to Step 15Go to Step 4
41. Ignition ªOFFº.
2. Raise the vehicle.
3. Disconnect the Bank 1 HO2S 2 electrical connector.
4. Using a test light connected to a good ground (do
not use Bank 1 HO2S 2 heater ground or Bank 1
HO2S 2 low), probe the ignition feed circuit at the
Bank 1 HO2S 2 electrical connector (PCM harness
side).
Does the test light illuminate?
ÐGo to Step 5Go to Step 7
5Connect the test light between the Bank 1 HO2S 2
ignition feed and the Bank 1 HO2S 2 heater ground.
Does the test light illuminate?
ÐGo to Step 6Go to Step 8