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Isuzu Rodeo UE. Manual - part 193

6E1–143

RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

(Cont'd)

Step

Yes

Value(s)

Action

Compare engine coolant temperature displayed on the
Tech 2 to the actual coolant temperature measured
with a thermometer. (Observe normal precautions
when opening the cooling system.)

Is the Tech 2 engine coolant temperature indication
close to the measured temperature?

—

Go to Step 9

Go to Step 7

1. Ignition OFF.
2. Disconnect the PCM.
3. Using a DVM, measure the resistance of the ECT at

the PCM connector.

4. Compare the DVM reading with the chart in ”Test

Description.”

Is the chart value approximately equal to the
thermometer reading?

—

Go to Step 12

Go to Step 8

Check for the following conditions in the wiring between
the ECT and the PCM:

An open circuit

A short to ground

A short to voltage

—

Go to Step 10

Go to Step 11

Refer to Cooling and Radiator for cooling system
diagnosis and repair condition as necessary.

Is the action complete?

—

Verify Repair

—

Replace the faulty terminal(s) or repair faulty wiring as
necessary.

Is the action complete?

—

Verify Repair

—

Replace the ECT sensor.

Is the action complete?

—

Verify Repair

—

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

—

6E1–144

RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DIAGNOSTIC TROUBLE CODE (DTC) P0131 O2 SENSOR CIRCUIT LOW VOLT-

AGE (BANK 1 SENSOR 1)

D06RX046

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 mega

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 ”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
excessively low for an extended period of time,
Diagnostic Trouble Code P0131 will be set. DTC P0131 is
a type A code.

Conditions for Setting the DTC

No related Diagnostic Trouble Codes.

Vehicle is operating in ”Closed Loop”.

Engine coolant temperature is above 60

C (140

”Closed Loop” commanded air/fuel ratio is between
14.5 and 14.8.

Throttle angle is between 3% and 19%.

All above conditions met for 0.3 seconds and the following
condition is met:

Bank 1 HO2S 1 signal voltage remains below 22 mV
during normal ”Closed Loop” operation for a total of
76.5 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.

”Open Loop” fuel control will be in effect.

Conditions for Clearing 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 Diagnostic Trouble Code P0131 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.

Diagnostic Trouble Code P0131 can be cleared by
using the Scan Tool’s ”Clear Info” function.

Diagnostic Aids

Check for the following conditions:

Heated oxygen sensor wiring – The sensor pigtail may
be routed incorrectly and/or contacting the exhaust
system. Also, check for shorts to ground, shorts to
battery positive and open circuits.

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 Diagnostic

6E1–145

RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Trouble Code P0131 may be set. Refer to Fuel System
Diagnosis.

Lean injector(s) – Perform ”Injector Balance Test.”

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
exhaust leaks that may cause a false lean condition to
be indicated.

Fuel contamination – Water, even in small amounts,
can be delivered to the fuel injectors. The water can
cause a lean exhaust to be indicated. Excessive
alcohol in the fuel can also cause this condition. For the
procedure to check for fuel contamination, Refer to
Fuel System Diagnosis.

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. Diagnostic Trouble Code P0131 failing during

operation may indicate a condition described in the
”Diagnostic Aids” above. If the Diagnostic Trouble
Code P0131 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 Diagnostic Trouble Code to
be set occurs. This may assist in diagnosing the
condition.

DTC P0131 – O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

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 Diagnostic
Trouble Code” criteria included in Diagnostic
Support.

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

Does the Bank 1 HO2S 1 voltage remain below the
specified value?

300 mV

Go to Step 4

Go to Step 3

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 “Diagnostic Trouble Code”

info for Diagnostic Trouble Code P0131 until the
Diagnostic Trouble Code P0131 test runs.

Note test result.

Does Tech 2 indicate DTC P0131 failed this ignition?

—

Go to Step 4

Refer to

Diagnostic

Aids

1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Check the Bank 1 HO2S 1 high and low circuits for a

short to ground or a short to the heater ground
circuit.

Are the Bank 1 HO2S 1 signal circuits shorted to
ground?

—

Go to Step 5

Go to Step 6

Repair the Bank 1 HO2S 1 signal circuit.

Is the action complete?

—

Verify repair

—

6E1–146

RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0131 – O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

(Cont'd)

Step

Yes

Value(s)

Action

1. Turn the ignition OFF HO2S 1 and PCM

disconnected.

2. Check for continuity between the high and low

signal circuits.

Was there continuity between the high and low circuits?

—

Go to Step 7

Go to Step 8

Repair the short between the high and low circuits.

Is the action complete?

—

Verify repair

—

1. Ignition OFF.
2. Reconnect the PCM, leave the sensor

disconnected.

3. Ignition ON.

Does the Tech 2 indicate Bank 1 HO2S 1 voltage near
the specified value?

430–450 mV

Refer to

Diagnostic

Aids

Go to Step 9

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

—

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