Infiniti QX56 (JA60). Manual - part 378

EC-164

< COMPONENT DIAGNOSIS >

[VK56DE]

P0138, P0158 HO2S2

Refer to 

EC-85, "Ground Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

2.

CLEAR THE SELF-LEARNING DATA

 With CONSULT-III

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

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

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 or P0175 detected?

Is it difficult to start engine?

 Without CONSULT-III

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

2. Turn ignition switch OFF.

3. Disconnect mass air flow sensor harness connector, and restart

and run engine for at least 5 seconds at idle speed.

4. Stop engine and reconnect mass air flow sensor harness con-

nector.

5. Make sure DTC P0102 is displayed.

6. Erase the DTC memory. Refer to 

EC-55, "Malfunction Indicator

Lamp (MIL)"

.

7. Make sure DTC P0000 is displayed.

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

Is the 1st trip DTC P0172 or P0175 detected?

Is it difficult to start engine?

Yes or No

Yes

>> Perform trouble diagnosis for DTC P0172, P0175. Refer to 

EC-177

.

No

>> GO TO 3.

3.

CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT

1. Turn ignition switch OFF.

2. Disconnect heated oxygen sensor 2 harness connector.

3. Disconnect ECM harness connector.

4. Check harness continuity between ECM terminal 78 and HO2S2 terminal 4.

Refer to Wiring Diagram.

BBIA0354E

BBIA0368E

BBIA0435E

P0138, P0158 HO2S2

EC-165

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

OK

>> GO TO 4.

NG

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

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 power.
OK or NG

OK

>> GO TO 5.

NG

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

5.

CHECK HEATED OXYGEN SENSOR 2

Refer to 

EC-165, "Component Inspection"

.

OK or NG

OK

>> GO TO 6.

NG

>> Replace malfunctioning heated oxygen sensor 2.

6.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-35, "How to Check Terminal"

 and 

GI-38, "Intermittent Incident"

.

>> INSPECTION END

Component Inspection

INFOID:0000000005149183

HEATED OXYGEN SENSOR 2

 With CONSULT-III

1. Turn ignition switch ON and select “DATA MONITOR” mode with CONSULT-III.
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.

Continuity should exist.

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.

EC-166

< COMPONENT DIAGNOSIS >

[VK56DE]

P0138, P0158 HO2S2

6. Select “FUEL INJECTION” in “ACTIVE TEST” mode, and select “HO2S2 (B1)/(B2)” as the monitor item

with CONSULT-III.

7. Check “HO2S2 (B1)/(B2)” at idle speed when adjusting “FUEL INJECTION” to 

±25%.

“HO2S2 (B1)/(B2)” should be above 0.58 V at least once when the “FUEL INJECTION” is +25%.

“HO2S2 (B1)/(B2)” should be below 0.18 V at least once when the “FUEL INJECTION” is 

−25%.

CAUTION:

• Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7

in) onto a hard surface such as a concrete floor; use a new one.

• Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread

Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.

 Without CONSULT-III

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 55 [HO2S2 (B1) signal] or 74 [HO2S2 (B2) signal] and

ground.

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 0.58 V and below 0.18 V at

least once during this procedure.

If the voltage can be confirmed at step 6, step 7 is not nec-

essary.

7. Keep vehicle at idling for 10 minutes, then check voltage. Or

check the voltage when coasting from 80 km/h (50 MPH) in D

position.

The voltage should be above 0.58 V and below 0.18 V at

least once during this procedure.

8. If NG, replace heated oxygen sensor 2.

CAUTION:

• Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7

in) onto a hard surface such as a concrete floor; use a new one.

• Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread

Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.

JMBIA0605GB

PBIB2054E

P0139, P0159 HO2S2

EC-167

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P0139, P0159 HO2S2

Component Description

INFOID:0000000005149184

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

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 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:0000000005149185

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 oxy-

gen storage capacity of the three way catalyst (manifold) causes the

longer switching time. To judge the malfunctions of heated oxygen

sensor 2, ECM monitors whether the switching response of the sen-

sor's voltage is faster than specified during the various driving condi-

tion such as fuel-cut.

DTC Confirmation Procedure

INFOID:0000000005149186

NOTE:

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure

before conducting the next step.
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.

 WITH CONSULT-III

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-III.
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).

SEF327R

SEF302U

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0139
0139
(Bank 1)

Heated oxygen sensor 2 
circuit slow response

It takes more time for the sensor to respond be-
tween rich and lean than the specified time.

• Harness or connectors

(The sensor circuit is open or shorted)

• Heated oxygen sensor 2
• Fuel pressure
• Fuel injector
• Intake air leaks

P0159
0159
(Bank 2)