Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 847

6E–117

3.2L ENGINE DRIVEABILITY AND EMISSIONS

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
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 “ON,” engine “OFF.” 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 white 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 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 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 “deceleration fuel cutoff

mode” operation may indicate a condition described
in the “Diagnostic Aids” 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.

6E–118

3.2L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0132 – HO2S Circuit High Voltage

Step

Action

Value(s)

Yes

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to

Step 2

Go to

OBD

System

Check

1. Install the Tech 2.
2. Run the engine at operating temperature.
3. Operate the vehicle within parameters specified

under “Conditions for Setting the DTC” included in
Diagnostic Support.

4. Using a Tech 2, monitor HO2S voltage.

Does the HO2S voltage remain above the specified
value?

952 mV (500

mV in

deceleration

fuel cutoff

mode)

Go to

Step 4

Go to

Step 3

1. Ignition “ON,” review and record Tech 2 Failure

Records data.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor “DTC” 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?

—

Go to

Step 4

Refer to

Diagnostic

Aids

1. Ignition “OFF.”
2. Disconnect HO2S.
3. Ignition “ON.”
4. At HO2S Sensor connector (ECM side) use a DVM

to measure voltages at the high and low signal
terminals.

Are the voltages in the specified range?

3-4 V

Go to

Step 5

Go to

Step 6

Repair short to voltage in signal circuit.

Is the action complete?

—

Verify repair

—

1. Ignition “ON,” engine“OFF.”
2. At HO2S connector (ECM side) jumper both the

HO2S high and low signal circuits (ECM side) to
ground.

3. Using a Tech 2, monitor HO2S voltage.

Is HO2S voltage below the specified value?

10 mV

Go to

Step 7

Go to

Step 8

1. Disconnect the jumpers to ground from HO2S

ECM-side connector.

2. With the HO2S connector disconnected, monitor

HO2S voltage.

Is HO2S voltage between the specified values?

425-475 mV

Refer to

Diagnostic

Aids

Go to

Step 8

Replace the ECM.

Is the action complete?

—

Verify repair

—

6E–119

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0134 (Flash DTC=15) HO2S Circuit

Insufficient Activity

060RW054

Circuit Description

The Engine Control Module ECM 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 ECM constantly monitors the
HO2S signal during “closed loop” 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.

Conditions for Setting the DTC

No related DTCs.

Engine run time is longer than 2 seconds.

Vehicle speed more than 60 Km/H.

ECT reading more than 70

The O

sensor voltage is between 350m volts and

600m volts.

Above conditions present for at least second.

Action Take 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.

“Open loop” fuel control will be in effect.

Conditions for Clearing the MIL/DTC

The ECM will turn the MIL “OFF” 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 “Clear
Info” function or by disconnecting the ECM battery
feed.

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
“ON,” engine “OFF,” 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

6E–120 3.2L ENGINE DRIVEABILITY AND EMISSIONS

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 “ON,” 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 condition is indicated.

DTC P0134 –HO2S Circuit Insufficient Activity

Step

Action

Value(s)

Yes

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to

Step 2

Go to

OBD

System

Check

1. 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 HO2S voltage varying outside
the specified values?

400-500 mV

Go to

Step 3

Go to

Step 4

1. Ignition “ON,” engine “OFF,” 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 “DTC” 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?

—

Go to

Step 4

Refer to

Diagnostic

Aids

Check for a damaged harness.

Was a problem found?

—

Verify repair

Go to

Step 5

Check for poor HO2S 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?

—

Verify repair

Go to

Step 6

Check for poor HO2S high and low circuit terminal
connections at the ECM and replace terminals if
necessary.

Did any terminals require replacement?

—

Verify repair

Go to

Step 7

1. Ignition “OFF.”
2. With the ECM disconnected, check continuity of the

HO2S high circuit.

3. If the HO2S high circuit measures over 5.0 ohms,

repair open or poor connection as necessary.

Was a HO2S high circuit problem found and corrected?

—

Verify repair

Go to

Step 8

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