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Nissan Frontier. Manual - part 410

P0138 HO2S2

EC-211

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0138 HO2S2

Component Description

INFOID:0000000009480871

The heated oxygen sensor 2, after three way catalyst (manifold),

monitors the oxygen level in the exhaust gas.

Even if switching characteristics of the A/F sensor 1 are shifted, the

air-fuel ratio is controlled to stoichiometric, by the signal from the

heated oxygen sensor 2.

This sensor is made of ceramic zirconia. The zirconia generates volt-

age from approximately 1V in richer conditions to 0V in leaner condi-

tions.

Under normal conditions the heated oxygen sensor 2 is not used for

engine control operation.

On Board Diagnosis Logic

INFOID:0000000009480872

The heated oxygen sensor 2 has a much longer switching time between rich and lean than the air fuel ratio (A/

F) sensor 1. The oxygen storage capacity of the three way catalyst (manifold) causes the longer switching

time.

MALFUNCTION A

To judge the malfunctions of heated oxygen sensor 2, ECM monitors

whether the voltage is unusually high during various driving condi-

tions such as fuel cut.

MALFUNCTION B

To judge the malfunctions of heated oxygen sensor 2, ECM monitors

whether the minimum voltage of sensor is sufficiently low during var-

ious driving conditions such as fuel cut.

SEF327R

PBIB1848E

PBIB2376E

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0138
0138

Heated oxygen sensor 2
circuit high voltage

An excessively high voltage from the sensor
is sent to ECM.

• Harness or connectors

(The sensor circuit is open or shorted)

• Heated oxygen sensor 2

The minimum voltage from the sensor is not
reached to the specified voltage.

• Harness or connectors

(The sensor circuit is open or shorted)

• Heated oxygen sensor 2
• Fuel pressure
• Fuel injector

EC-212

< DTC/CIRCUIT DIAGNOSIS >

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P0138 HO2S2

DTC Confirmation Procedure

INFOID:0000000009480873

Perform PROCEDURE FOR MALFUNCTION A first.

If DTC cannot be confirmed, perform PROCEDURE FOR MALFUNCTION B.

NOTE:

If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at

least 10 seconds before conducting the next test.

PROCEDURE FOR MALFUNCTION A

With CONSULT

1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
4. Let engine idle for 2 minutes.
5. Check 1st trip DTC.
6. If 1st trip DTC is detected, go to

EC-213, "Diagnosis Procedure"

With GST

Follow the procedure “WITH CONSULT” above.

PROCEDURE FOR MALFUNCTION B

With CONSULT

TESTING CONDITION:

For better results, perform DTC WORK SUPPORT at a temperature of 0 to 30

°C (32 to 86 °F).

1. Turn ignition switch ON and select “DATA MONITOR” mode with CONSULT.
2. Start engine and warm it up to the normal operating temperature.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
5. Let engine idle for 1 minute.
6. Make sure that “COOLAN TEMP/S” indicates more than 70

°C (158°F).

If not, warm up engine and go to next step when “COOLAN TEMP/S” indication reaches 70

°C (158°F).

7. Open engine hood.
8. Select “HO2S2 (B1) P1146” of “HO2S2” in “DTC WORK SUPPORT” mode with CONSULT.
9. Start engine and following the instruction of CONSULT display.

NOTE:

It will take at most 10 minutes until “COMPLETED” is displayed.

10. Make sure that “OK” is displayed after touching “SELF-DIAG RESULTS”.

If “NG” is displayed, refer to

EC-213, "Diagnosis Procedure"

If “CAN NOT BE DIAGNOSED” is displayed, perform the following.

a. Turn ignition switch OFF and leave the vehicle in a cool place (soak the vehicle).
b. Return to step 1.

Overall Function Check

INFOID:0000000009480874

Use this procedure to check the overall function of the heated oxygen sensor 2 circuit. During this check, a 1st

trip DTC might not be confirmed.

PROCEDURE FOR MALFUNCTION B

With GST

1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
4. Let engine idle for 1 minute.
5. Set voltmeter probes between ECM terminal 33 (HO2S2 signal) and ground.

P0138 HO2S2

EC-213

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

6. Check the voltage when revving up to 4,000 rpm under no load at least 10 times.

(Depress and release accelerator pedal as soon as possible.)

The voltage should be above 0.78V and below 0.18V at least once during this procedure.

If the voltage can be confirmed in step 6, step 7 is not necessary.

7. Keep vehicle at idling for 10 minutes, then check the voltage. Or check the voltage when coasting from 80

km/h (50 MPH) in D position (A/T), 4th gear position (M/T).

The voltage should be above 0.78V and below 0.18V at least once during this procedure.

8. If NG, go to

EC-213, "Diagnosis Procedure"

Diagnosis Procedure

INFOID:0000000009480875

PROCEDURE FOR MALFUNCTION A

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

2. Loosen and retighten three ground screws on the body. Refer to

EC-149, "Ground Inspection"

OK or NG

>> GO TO 2.

>> Repair or replace ground connections.

CHECK HO2S2 CONNECTOR FOR WATER

1. Disconnect heated oxygen sensor 2 harness connector.

2. Check that water is not inside connectors.
OK or NG

>> GO TO 3.

>> Repair or replace harness or connectors.

CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT

1. Disconnect heated oxygen sensor 2 harness connector.

2. Disconnect ECM harness connector.

3. Check harness continuity between HO2S2 terminal 4 and ECM

terminal 35.

Refer to Wiring Diagram.

4. Also check harness for short to ground and short to power.
OK or NG

>> GO TO 4.

>> Repair open circuit, short to ground or short to ground or

short to power in harness or connectors.

CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1. Check harness continuity between ECM terminal 33 and HO2S2 terminal 1.

Refer to Wiring Diagram.

2. Check harness continuity between ECM terminal 33 or HO2S2 terminal 1 and ground.

Refer to Wiring Diagram.

BBIA0614E

Continuity should exist.

BBIA0613E

Continuity should exist.

EC-214

< DTC/CIRCUIT DIAGNOSIS >

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P0138 HO2S2

3. Also check harness for short to power.
OK or NG

>> GO TO 5.

>> Repair open circuit, short to ground or short to power in harness or connectors.

CHECK HEATED OXYGEN SENSOR 2

Refer to

EC-216, "Component Inspection"

OK or NG

>> GO TO 6.

>> Replace heated oxygen sensor 2. Refer to

EX-5, "Exploded View"

CHECK INTERMITTENT INCIDENT

Refer to

GI-42, "Intermittent Incident"

>> INSPECTION END

PROCEDURE FOR MALFUNCTION B

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

2. Loosen and retighten three ground screws on the body. Refer to

EC-149, "Ground Inspection"

OK or NG

>> GO TO 2.

>> Repair or replace ground connections.

CLEAR THE SELF-LEARNING DATA

With CONSULT

1. Start engine and warm it up to normal operating temperature.

2. Select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CONSULT.

3. Clear the self-learning control coefficient by touching “CLEAR”.

4. Run engine for at least 10 minutes at idle speed.

Is the 1st trip DTC P0172 detected?

Is it difficult to start engine?

Without CONSULT

1. Start engine and warm it up to normal operating temperature.

2. Turn ignition switch OFF.

Continuity should not exist.

BBIA0614E

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