Infiniti Q45. Manual - part 414

DTC P0138, P0158 HO2S2

EC-295

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EC

Specification data are reference values and are measured between each terminal and ground.

CAUTION:

Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.

Diagnostic Procedure

NBS001UU

PROCEDURE FOR MALFUNCTION A

1. 

CHECK GROUND CONNECTIONS

1.

Turn ignition switch OFF.

2.

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

EC-154, "Ground Inspection"

 .

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

TER-

MINAL 

NO.

WIRE 

COLOR

ITEM

CONDITION

DATA (DC Voltage)

25

G

Heated oxygen sensor 2 
heater (bank 2)

[Engine is running]

●

Engine speed: Below 3,600 rpm after the 
following conditions are met

–

Engine: After warming up

–

Keeping the engine speed between 3,500 
and 4,000 rpm for 1 minute and at idle for 1 
minute under no load

0 - 1.0V

[Ignition switch: ON]

●

Engine stopped

[Engine is running]

●

Engine speed: Above 3,600 rpm

BATTERY VOLTAGE
(11 - 14V)

74

B

Heated oxygen sensor 2 
(bank 2)

[Engine is running]

●

Revving engine from idle to 3,000 rpm 
quickly after the following conditions are met

–

Engine: After warming up

–

After keeping the engine speed between 
3,500 and 4,000 rpm for 1 minute and at idle 
for 1 minute under no load

0 - Approximately 1.0V

78

OR

Sensor ground
(Heated oxygen sensor 2)

[Engine is running]

●

Warm-up condition

●

Idle speed

Approximately 0V

PBIB2417E

EC-296

DTC P0138, P0158 HO2S2

2. 

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 78.
Refer to Wiring Diagram.

4.

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

OK or NG

OK

>> GO TO 4.

NG

>> GO TO 3.

3. 

DETECT MALFUNCTIONING PART

Check the following.

●

Harness connectors E315, F5

●

Harness for open or short between heated oxygen sensor 2 and ECM

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

Continuity should exist.

PBIB0018E

DTC P0138, P0158 HO2S2

EC-297

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EC

4. 

CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1.

Check harness continuity between ECM terminal and HO2S2 terminal as follows.
Refer to Wiring Diagram.

2.

Check harness continuity between the following terminals and ground.
Refer to Wiring Diagram.

3.

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

OK or NG

OK

>> GO TO 6.

NG

>> GO TO 5.

5. 

DETECT MALFUNCTIONING PART

Check the following.

●

Harness connectors E315, F5

●

Harness for open or short between heated oxygen sensor 2 and ECM

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

6. 

CHECK HO2S2 CONNECTOR FOR WATER

1.

Turn ignition switch OFF.

2.

Disconnect heated oxygen sensor 2 harness connector.

3.

Check connectors for water.

OK or NG

OK

>> GO TO 7.

NG

>> Repair or replace harness or connectors.

7. 

CHECK HEATED OXYGEN SENSOR 2

Refer to 

EC-302, "Component Inspection"

 .

OK or NG

OK

>> GO TO 8.

NG

>> Replace malfunctioning heated oxygen sensor 2.

DTC

Terminals

Bank

ECM

Sensor

P0138

55

1

1

P0158

74

1

2

Continuity should exist.

DTC

Terminals

Bank

ECM

Sensor

P0138

55

1

1

P0158

74

1

2

Continuity should not exist.

Water should not exist.

EC-298

DTC P0138, P0158 HO2S2

8. 

CHECK INTERMITTENT INCIDENT

Refer to 

EC-145, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

 .

>> INSPECTION END

PROCEDURE FOR MALFUNCTION A

1. 

CHECK GROUND CONNECTIONS

1.

Turn ignition switch OFF.

2.

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

EC-154, "Ground Inspection"

 .

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

PBIB2417E