Infiniti FX35, FX50 (S51). Manual - part 670

P0138, P0158 HO2S2

EC-221

< DTC/CIRCUIT DIAGNOSIS >

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P0138, P0158 HO2S2

Description

INFOID:0000000005236824

The heated oxygen sensor 2, after three way catalyst 1, monitors the
oxygen level in the exhaust gas on each bank.
Even if switching characteristics of the air fuel ratio (A/F) sensor 1
are shifted, the air-fuel ratio is controlled to stoichiometric, by the sig-
nal from the heated oxygen sensor 2.
This sensor is made of ceramic zirconia. The zirconia generates volt-
age from approximately 1 V in richer conditions to 0 V in leaner con-
ditions.
Under normal conditions the heated oxygen sensor 2 is not used for
engine control operation.

DTC Logic

INFOID:0000000005236825

DTC DETECTION LOGIC

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 1 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

Heated oxygen sensor 2 
(bank 1) circuit high volt-
age

A)

An excessively high voltage from the sen-
sor is sent to ECM.

• Harness or connectors

(The sensor circuit is open or shorted)

• Heated oxygen sensor 2

B)

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-222

< DTC/CIRCUIT DIAGNOSIS >

[VQ35HR]

P0138, P0158 HO2S2

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure
before conducting the next test.
1.

Turn ignition switch OFF and wait at least 10 seconds.

2.

Turn ignition switch ON.

3.

Turn ignition switch OFF and wait at least 10 seconds.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION A

1.

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

2.

Turn ignition switch OFF and wait at least 10 seconds.

3.

Turn ignition switch ON.

4.

Turn ignition switch OFF and wait at least 10 seconds.

5.

Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.

6.

Let engine idle for 2 minutes.

7.

Check 1st trip DTC.

Is 1st trip DTC detected?

YES

>> Go to 

EC-224, "Diagnosis Procedure"

.

NO-1

>> With CONSULT-III: GO TO 3.

NO-2

>> With GST: GO TO 5.

3.

PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION B

With CONSULT-III

NOTE:
For better results, perform “DTC WORK SUPPORT” at a temperature of 0 to 30 

°

C (32 to 86 

°

F).

1.

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

2.

Turn ignition switch OFF and wait at least 10 seconds.

3.

Turn ignition switch ON.

4.

Turn ignition switch OFF and wait at least 10 seconds.

5.

Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.

6.

Let engine idle for 1 minute.

7.

Select “DATA MONITOR” mode with CONSULT-III.

8.

Check 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).

9.

Open engine hood.

10. Select “HO2S2 (B1) P1146” (for DTC P0138) or “HO2S2 (B2) P1166” (for DTC P0158) of “HO2S2” in

“DTC WORK SUPPORT” mode with CONSULT-III.

11. Follow the instruction of CONSULT-III display.

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

12. Touch “SELF-DIAG RESULTS”.

Which is displayed on CONSULT-III screen?

OK

>> INSPECTION END

NG

>> Go to 

EC-224, "Diagnosis Procedure"

.

CON NOT BE DIAGNOSED>>GO TO 4.

P0158

Heated oxygen sensor 2 
(bank 2) circuit high volt-
age

A)

An excessively high voltage from the sen-
sor is sent to ECM.

• Harness or connectors

(The sensor circuit is open or shorted)

• Heated oxygen sensor 2

B)

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

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0138, P0158 HO2S2

EC-223

< DTC/CIRCUIT DIAGNOSIS >

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4.

PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION B AGAIN

1.

Turn ignition switch OFF and leave the vehicle in a cool place (soak the vehicle).

2.

Perform DTC confirmation procedure again.

>> GO TO 3.

5.

PERFORM COMPONENT FUNCTION CHECK FOR MALFUNCTION B

With GST

Perform component function check. Refer to 

EC-223, "Component Function Check"

.

NOTE:
Use component function check to check the overall function of the heated oxygen sensor 2 circuit. During this
check, a 1st trip DTC might not be confirmed.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Go to 

EC-224, "Diagnosis Procedure"

.

Component Function Check

INFOID:0000000005236826

1.

PERFORM COMPONENT FUNCTION CHECK-I

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.

Turn ignition switch ON.

4.

Turn ignition switch OFF and wait at least 10 seconds.

5.

Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.

6.

Let engine idle for 1 minute.

7.

Check the voltage between ECM harness connector terminals under the following condition.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> GO TO 2.

2.

PERFORM COMPONENT FUNCTION CHECK-II

Check the voltage between ECM harness connector terminals under the following condition.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> GO TO 3.

3.

PERFORM COMPONENT FUNCTION CHECK-III

Check the voltage between ECM harness connector terminals under the following condition.

DTC

ECM

Condition

Voltage

Connector

+

–

Terminal

Terminal

P0138

F102

76

84

Revving up to 4,000 rpm under no load at 
least 10 times

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

P0158

80

DTC

ECM

Condition

Voltage

Connector

+

–

Terminal

Terminal

P0138

F102

76

84

Keeping engine at idle for 10 minutes

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

P0158

80

EC-224

< DTC/CIRCUIT DIAGNOSIS >

[VQ35HR]

P0138, P0158 HO2S2

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Go to 

EC-224, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000005236827

1.

INSPECTION START

Confirm the detected malfunction (A or B). Refer to 

EC-221, "DTC Logic"

.

Which malfunction is detected?

A

>> GO  TO  2

B

>> GO  TO  9.

2.

CHECK GROUND CONNECTION

1.

Turn ignition switch OFF.

2.

Check ground connection M95. Refer to Ground Inspection in 

GI-39, "Circuit Inspection"

.

Is the inspection result normal?

YES

>> GO TO 3.

NO

>> Repair or replace ground connection.

3.

CHECK HEATED OXYGEN SENSOR 2 (HO2S2) CONNECTOR FOR WATER

1.

Disconnect HO2S2 harness connector.

2.

Check that water is not inside connectors.

Is the inspection result normal?

YES

>> GO TO 4.

NO

>> Repair or replace harness or connectors.

4.

CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT

1.

Disconnect HO2S2 harness connector.

2.

Disconnect ECM harness connector.

3.

Check the continuity between HO2S2 harness connector and ECM harness connector.

4.

Also check harness for short to ground and short to power.

Is the inspection result normal?

YES

>> GO TO 5.

NO

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

5.

CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1.

Check the continuity between HO2S2 harness connector and ECM harness connector.

DTC

ECM

Condition

Voltage

Connector

+

–

Terminal

Terminal

P0138

F102

76

84

Coasting from 80 km/h (50 MPH) in D po-
sition

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

P0158

80

DTC

HO2S2

ECM

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0138

1

F54

1

F102

84

Existed

P0158

2

F53

1

DTC

HO2S2

ECM

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0138

1

F54

4

F102

76

Existed

P0158

2

F53

4

80