Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 289

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 “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 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
“Diagnostic Aids” 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

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 the parameters specified

under “Conditions for Setting the DTC” 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 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 P0138

until the DTC P0138 test runs.

4. Note the test result.

Does the Tech 2 indicate DTC P0138 failed this
ignition?

—

Go to

Step 4

Refer to

Diagnostic

Aids

1. Ignition “OFF”.
2. Disconnect Bank 1 HO2S 1.
3. Ignition “ON”.
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 V

Go to

Step 5

Go to

Step 6

6E–187

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0138 – HO2S Circuit High Voltage Bank 1 Sensor 2

(Cont'd)

Step

Yes

Value(s)

Action

Repair short to voltage in the signal circuit.

Is the action complete?

—

Verify repair

—

1. Ignition “ON”, engine“OFF”.
2. At Bank 1 HO2S 2 connector (PCM side) jumper

both the HO2S high and low signal circuits (PCM
side) to ground.

3. Using a Tech 2, monitor Bank 1 HO2S 2 voltage.

Is Bank 1 HO2S 2 voltage below the specified value?

10 mV

Go to

Step 7

Go to

Step 8

1. Disconnect the jumpers to ground from Bank 1

HO2S 2 PCM–side connector.

2. With the HO2S 2 connector disconnected, monitor

BANK 1 HO2S 2 voltage.

Is the Bank 1 HO2S 2 voltage between the specified
values?

425-475 mV

Refer to

Diagnostic

Aids

Go to

Step 8

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed. Refer to

On-Vehicle Service in

Powertrain Control Module and Sensors for
procedures.

And also refer to latest Service Bulletin.

Check to see if the Latest software is released or not.
And then Down Load the LATEST PROGRAMMED
SOFTWARE to the replacement PCM.

Is the action complete?

—

Verify repair

—

6E–188

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code(DTC)

P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2

060R200054

Circuit Description

To control emissions of hydrocarbons (HC), carbon
monoxide (CO), and oxides of nitrogen (NOx), a
three-way catalytic converter is used. The catalyst within
the converter promotes a chemical reaction which
oxidizes the HC and CO present in the exhaust gas,
converting them into harmless water vapor and carbon
dioxide. The catalyst also reduces NOx, converting it to
nitrogen. The powertrain control module (PCM) has the
ability to monitor this process using the Bank 1 HO2S 1
and the Bank 1 HO2S 2 heated oxygen sensors. The
Bank 1 HO2S 2 sensor produces an output signal which
indicates the amount of oxygen present in the exhaust
gas entering the three-way catalytic converter. The Bank
1 HO2S 2 sensor produces an output signal which
indicates the oxygen storage capacity of the catalyst; this
in turn indicates the catalyst’s ability to convert exhaust
gases efficiently. If catalyst is operating efficiently, the
Bank 1 HO2S 1 signal will be far more active than that
produced by the Bank 1 HO2S 2 sensor. If the Bank 1
HO2S 2 signal voltage remains between 400 mV and
500 mV for an extended period of time, DTC P0140 will be
set. Heated oxygen sensors are used to minimize the
amount of time required for “closed loop” 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.

Engine coolant temperature is above 60

C (140

F).

The engine has been running for over 5 seconds.

Oxygen sensor heater is functioning properly.

Engine is operating in “closed loop”

Bank 1 HO2S 2 signal voltage remains between
426 mV and 474 mV for a total of 106 seconds over a
125-second period of time.

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 Cleaning the MIL/DTC

The PCM 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 P0140 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0140 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

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
ignition“ON”, engine “OFF”, 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 “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 P0140 test passes while the Failure

Records conditions are being duplicated, an
intermittent condition is indicated.

DTC P0140 – HO2S Circuit Insufficient Activity BANK 1 SENSOR 2

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 Bank 1 HO2S 2 voltage
varying outside the specified values?

425-475 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 P0140

until the DTC P0140 test runs.

4. Note the test result.

Does the Tech 2 indicate DTC P0140 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 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?

—

Verify repair

Go to

Step 6

Check 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?

—

Verify repair

Go to

Step 7

1. Ignition “OFF”.
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?

—

Verify repair

Go to

Step 8

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