Nissan Pathfinder (2008 year). Manual - part 257

P0139, P0159 HO2S2

EC-173

< COMPONENT DIAGNOSIS >

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P0139, P0159 HO2S2

Component Description

INFOID:0000000001375904

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:0000000001375906

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 before the three way catalyst (manifold) causes
the longer switching time. To judge the malfunctions of heated oxy-
gen sensor 2, ECM monitors whether the switching response of the
sensor's voltage is faster than specified during the various driving
condition such as fuel-cut.

DTC Confirmation Procedure

INFOID:0000000001375907

NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing 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.

Turn ignition switch ON.

5.

Turn ignition switch OFF and wait at least 10 seconds.

6.

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

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)

EC-174

< COMPONENT DIAGNOSIS >

[VQ40DE]

P0139, P0159 HO2S2

7.

Let engine idle for 1 minute.

8.

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 to 70

°

C (158

°

F).

9.

Select “HO2S2 (B1) P0139” or “HO2S2 (B2) P0159” of “HO2S2” in “DTC WORK SUPPORT” mode with
CONSULT-III.

10. Start engine and following the instruction of CONSULT-III.

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

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

If “NG” is displayed, refer to 

EC-174, "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:0000000001375908

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.

 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.

Set voltmeter probes between ECM terminal 74 [HO2S2 (B1) signal] or 55 [HO2S2 (B2) signal] and
ground.

8.

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.)
A change of voltage should be more than 0.24V for 1 sec-
ond during this procedure.
If the voltage can be confirmed in step 6, step 7 is not nec-
essary.

9.

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 with “OD” OFF.
A change of voltage should be more than 0.24V for 1 sec-
ond during this procedure.

10. If NG, go to 

EC-174, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000001375910

1.

CHECK GROUND CONNECTIONS

1.

Turn ignition switch OFF.

2.

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

EC-96, "Ground Inspection"

.

PBIB1607E

BBIA0539E

P0139, P0159 HO2S2

EC-175

< COMPONENT DIAGNOSIS >

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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 P0171, P0172, P0174 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-54, "Emission-related

Diagnostic Information"

.

7.

Make sure DTC P0000 is displayed.

8.

Run engine for at least 10 minutes at idle speed.
Is the 1st trip DTC P0171, P0172, P0174 or P0175 detected?
Is it difficult to start engine?

Yes or No

Yes

>> Perform trouble diagnosis for DTC P0171, P0174 or P0172, P0175. Refer to 

EC-179, "On Board

Diagnosis Logic"

 or 

EC-185, "On Board Diagnosis Logic"

.

No

>> GO TO 3.

3.

CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT

1.

Turn ignition switch OFF.

BBIA0541E

EC-176

< COMPONENT DIAGNOSIS >

[VQ40DE]

P0139, P0159 HO2S2

2.

Disconnect heated oxygen sensor 2 harness connector.

3.

Disconnect ECM harness connector.

4.

Check harness continuity between HO2S2 terminal 4 and ECM terminal 78.
Refer to Wiring Diagram.

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.

Continuity should exist.

BBIA0540E

DTC

Terminals

Bank

ECM

Sensor

P0139

74

1

1

P0159

55

1

2

Continuity should exist.

DTC

Terminals

Bank

ECM

Sensor

P0139

74

1

1

P0159

55

1

2

Continuity should not exist.

P0139, P0159 HO2S2

EC-177

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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-177, "Component Inspection"

.

OK or NG

OK

>> GO TO 6.

NG

>> Replace malfunctioning heated oxygen sensor 2.

6.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-47, "Work Flow"

.

>> INSPECTION END

Component Inspection

INFOID:0000000001581260

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.

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 0.68V at least once when the “FUEL INJECTION” is +25%.
“HO2S2 (B1)/(B2)” should be below 0.18V 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 74 [HO2S2 (B1) signal] or 55 [HO2S2 (B2) signal] and
ground.

PBIB3458E

EC-178

< COMPONENT DIAGNOSIS >

[VQ40DE]

P0139, P0159 HO2S2

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 0.68V at least once during this
procedure.
If the voltage is above 0.68V at step 6, step 7 is not neces-
sary.

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 with “OD” OFF.
The voltage should be below 0.18V 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.

PBIB1607E

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-179

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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

On Board Diagnosis Logic

INFOID:0000000001375912

With the Air-Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the
theoretical mixture ratio based on the mixture ratio feedback signal from the air fuel ratio (A/F) sensor 1. The
ECM calculates the necessary compensation to correct the offset between the actual and the theoretical
ratios.
In case the amount of the compensation value is extremely large (the actual mixture ratio is too lean.), the
ECM judges the condition as the fuel injection system malfunction and lights up the MIL (2 trip detection logic).

DTC Confirmation Procedure

INFOID:0000000001375913

NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing 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

1.

Start engine and warm it up to 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.

Turn ignition switch ON and select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CON-
SULT-III.

6.

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

7.

Start engine again and let it idle for at least 10 minutes.

8.

Check 1st trip DTC.
The 1st trip DTC P0171 or P0174 should be detected at this stage, if a malfunction exists. If so, go to 

EC-

180, "Diagnosis Procedure"

.

NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.

a.

Turn ignition switch OFF and wait at least 10 seconds.

b.

Start engine and drive the vehicle under the similar conditions to (1st trip) Freeze Frame Data for 10 min-
utes. Refer to the table below.
Hold the accelerator pedal as steady as possible.
The similar conditions to (1st trip) Freeze Frame Data means the vehicle operation that the following con-
ditions should be satisfied at the same time.

Sensor

Input signal to ECM

ECM function

Actuator

A/F sensor 1

Density of oxygen in exhaust gas
(Mixture ratio feedback signal)

Fuel injection 
control

Fuel injector

DTC No.

Trouble diagnosis 

name

DTC detecting condition

Possible cause

P0171
0171
(Bank 1)

Fuel injection system 
too lean

• Fuel injection system does not operate properly.
• The amount of mixture ratio compensation is too 

large. (The mixture ratio is too lean.)

• Intake air leaks
• Air fuel ratio (A/F) sensor 1
• Fuel injector
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Mass air flow sensor
• Incorrect PCV hose connection

P0174
0174
(Bank 2)

EC-180

< COMPONENT DIAGNOSIS >

[VQ40DE]

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

9.

If it is difficult to start engine at step 6, the fuel injection system has a malfunction, too.

10. Crank engine while depressing accelerator pedal. If engine starts, go to 

EC-180, "Diagnosis Procedure"

. If

engine does not start, check exhaust and intake air leak visually.

 WITH GST

1.

Start engine and warm it up to 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.

Disconnect mass air flow sensor harness connector.

6.

Restart engine and let it idle for at least 5 seconds.

7.

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

8.

Select Service $03 with GST. Make sure DTC P0102 is
detected.

9.

Select Service $04 with GST and erase the DTC P0102.

10. Start engine again and let it idle for at least 10 minutes.
11. Select Service $07 with GST. The 1st trip DTC P0171 or P0174

should be detected at this stage, if a malfunction exists. If so, go
to 

EC-180, "Diagnosis Procedure"

.

NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.

a.

Turn ignition switch OFF and wait at least 10 seconds.

b.

Start engine and drive the vehicle under the similar conditions to (1st trip) Freeze Frame Data for 10 min-
utes. Refer to the table below.
Hold the accelerator pedal as steady as possible.

The similar conditions to (1st trip) Freeze Frame Data means the vehicle operation that the following con-
ditions should be satisfied at the same time.

12. If it is difficult to start engine at step 8, the fuel injection system has a malfunction.
13. Crank engine while depressing accelerator pedal. If engine starts, go to 

EC-180, "Diagnosis Procedure"

.

If engine does not start, check exhaust and intake air leak visually.

Diagnosis Procedure

INFOID:0000000001375915

1.

CHECK EXHAUST GAS LEAK

1.

Start engine and run it at idle.

Engine speed

Engine speed in the freeze frame data 

±

 400 rpm

Vehicle speed

Vehicle speed in the freeze frame data 

±

 10 km/h (6 MPH)

Engine coolant temperature (T) 
condition

When the freeze frame data shows lower than 70 

°

C (158 

°

F),

T should be lower than 70 

°

C (158 

°

F).

When the freeze frame data shows higher than or equal to 70 

°

C (158 

°

F),

T should be higher than or equal to 70 

°

C (158 

°

F).

BBIA0541E

Engine speed

Engine speed in the freeze frame data 

±

 400 rpm

Vehicle speed

Vehicle speed in the freeze frame data 

±

 10 km/h (6 MPH)

Engine coolant temperature (T) 
condition

When the freeze frame data shows lower than 70 

°

C (158 

°

F),

T should be lower than 70 

°

C (158 

°

F).

When the freeze frame data shows higher than or equal to 70 

°

C (158 

°

F),

T should be higher than or equal to 70 

°

C (158 

°

F).