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Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 225

ENGINE DRIVEABILITY AND EMISSIONS

6E–141

Using the DVM and check the TPS power supply
circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the TPS connector.

3. Check the circuit for short to voltage circuit.

Was the DVM indicated specified value?

Approximately

5.0V

Go to Step 9

Go to Step 8

Repair the short to voltage circuit between the ECM
and TPS.
Was the problem solved?

—

Verify repair

Go to Step 14

Using the DVM and check the TPS signal circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the TPS connector.

3. Check the circuit for short to power supply circuit.

Was the DVM indicated specified value?

Less than 1V

Go to Step 10

Repair faulty

harness and

verify repair

Using the DVM and check the TPS ground circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the TPS connector .

3. Check the circuit for short to power supply circuit.

Was the DVM indicated specified value?

Less than 1V

Go to Step 11

Repair faulty

harness and

verify repair

Step

Action

Value(s)

Yes

E68

E60(J1)

E68

6E–142

ENGINE DRIVEABILITY AND EMISSIONS

Using the DVM and check the TPS ground circuit.
Breaker box is available:

1. Ignition “Off”, engine “Off”.

2. Install the breaker box as type A. (ECM

disconnected) Ref. 6E-80.

3. Disconnect the TPS connector.

4. Check the circuit for open circuit.

Was the problem found?

Breaker box is not available:

1. Ignition “Off”, engine “Off”.

2. Disconnect the TPS connector and ECM

connector.

3. Check the circuit for open circuit.

Was the problem found?

—

Repair faulty

harness and

verify repair

Go to Step 14

Substitute a known good TPS and recheck.
Was the problem solved?

—

Go to Step 13

Go to Step 14

Replace the TPS.
Is the action complete?

—

Verify repair

—

Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”.
Was the problem solved?

—

Verify repair

Go to Step 14

Replace the ECM.
Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobiliser system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobiliser System-ECM replacement” for
the ECM/Immobiliser linking procedure.

—

Verify repair

—

Step

Action

Value(s)

Yes

E68

E60(J1)

E68

ENGINE DRIVEABILITY AND EMISSIONS

6E–143

DIAGNOSTIC TROUBLE CODE (DTC) P0131 O

SENSOR CIRCUIT LOW

VOLTAGE (BANK 1 SENSOR 1)

Condition for setting the DTC and action taken when the DTC sets

Circuit Description

The engine control module (ECM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) signal and low circuits. 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 excessively low for an
extended period of time, Diagnostic Trouble Code
P0131 will be set.

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.

Code

Type

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

P0131

SensorCircuit Low Voltage (Bank 1

Sensor 1)

1. No DTC relating to MAP sensor, TPS,

EVAP purge, ECT sensor, CKP sensor,
VSS, injector control circuit and ignition
control circuit.

2. Engine coolant temperature is more than

60°C.

3. O

sensor bank 1 output voltage is below

50mV in “Closed Loop” condition.

“Open Loop” fuel control.

µP

Ign

Crankshaft
Position
Sensor

J1-1 J1-2 J1-17

Battery
Voltage

2.0
WHT

ECM
10A

450
mV

A/D Converter

Vcc
+5V

TIMING
COVER

J2-6

J2-21

Fuel
Pump

FUEL
PUMP
20A

2.0
BLK

2.0
BLK/
BLU

Fuel
Pump
Relay

SENSOR
10A

Heated
O

Sensor

0.85
RED/
WHT

0.5
GRN/
WHT

0.5
RED/
WHT

0.5
BLU/
WHT

0.5
BLU

0.5 PNK

J2-31

J2-11

J2-2

J2-18

Engine
Control
Module
(ECM)

6E–144

ENGINE DRIVEABILITY AND EMISSIONS

• Poor ECM to engine block grounds.

• Fuel pressure - The system will go lean if pressure is

too low. The ECM can compensate for some
decrease. However, if fuel pressure is too low, a
Diagnostic 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.

Diagnostic Trouble Code (DTC) P0131

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 On Board

Diagnostic

(OBD) System

Check

1. Connect the Tech 2.

2. Review and record the failure information.

3. Select “F0: Read DTC Infor By Priority” in “F0:

Diagnostic Trouble Code”.

Is the DTC P0131 stored as “Present Failure”?

—

Go to Step 3

Refer to

Diagnostic Aids

and Go to Step

1. Using the Tech2, ignition “On” and engine “Off”.

2. Select “Clear DTC Information” with the Tech2 and

clear the DTC information.

3. Operate the vehicle and monitor the “F5: Failed

This Ignition” in “F2: DTC Information”.

Was the DTC P0131 stored in this ignition cycle?

—

Go to Step 4

Refer to

Diagnostic Aids

and Go to Step

Check for poor/faulty connection at the O

sensor or

ECM connector. If a poor/faulty connection is found,
repair as necessary.
Was the problem found?

—

Verify repair

Go to Step 5

Using the DVM and check the O

sensor circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the O

sensor connector.

3. Check the circuit for short to heater ground or

ground circuit.

Was the DVM indicated specified value?

Approximatly

450mV

Go to Step 7

Go to Step 6

C56(J2)

E77

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