2006 INFINITI QX56 engine

DTC P0137, P0157 HO2S2EC-257
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EC
Revision: November 2009 2006 QX56
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.
TER-
MINAL NO. WIRE
COLOR ITEM
CONDITION DATA (DC Voltage)
6GR Heated oxygen sensor 2
heater (bank 1) [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)
55 R Heated oxygen sensor 2
(bank 1) [Engine is running]

Revving engine from idle to 3,000 rpm
quickly 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 - Approximately 1.0V
78 B/W Sensor ground
(Heated oxygen sensor 2) [Engine is running]

Warm-up condition

Idle speed
Approximately 0V

DTC P0137, P0157 HO2S2EC-259
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Revision: November 2009 2006 QX56
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 ProcedureUBS00H8H
1. CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten three ground screws on the body. Refer to EC-150, "
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 O/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 L 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
–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 B/W Sensor ground
(Heated oxygen sensor 2) [Engine is running]

Warm-up condition

Idle speed
Approximately 0V
BBIA0354E

EC-260Revision: November 2009
DTC P0137, P0157 HO2S2
2006 QX56
2. CLEAR THE SELF-LEARNING DATA
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Select “SELF-LEARNING CONT ” in “WORK SUPPORT” mode
with CONSULT-II.
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 or P0174 detected?
Is it difficult to start engine?
Without CONSULT-II
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-61, "
HOW TO ERASE
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 or P0174 detected?
Is it difficult to start engine?
Ye s o r N o
Yes >> Perform trouble diagnosis for DTC P0171 or P0174. Refer to EC-288, "DTC P0171, P0174 FUEL
INJECTION SYSTEM FUNCTION" .
No >> GO TO 3.
SEF968Y
BBIA0368E

EC-262Revision: November 2009
DTC P0137, P0157 HO2S2
2006 QX56
5. CHECK HEATED OXYGEN SENSOR 2
Refer to EC-262, "
Component Inspection" .
OK or NG
OK >> GO TO 6.
NG >> Replace malfunctioning heated oxygen sensor 2.
6. CHECK INTERMITTENT INCIDENT
Refer to EC-144, "
TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT" .
>> INSPECTION END
Component InspectionUBS00H8I
HEATED OXYGEN SENSOR 2
With CONSULT-II
1. Turn ignition switch ON and select “DATA MONITOR ” mode with
CONSULT-II.
2. Start engine and warm it up to the normal operating tempera- ture.
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-II.
7. Check “HO2S2 (B1)/(B2) ” at idle speed when adjusting “FUEL INJECTION” to ±25%.
“HO2S2 (B1)/(B2)” should be above 0.58V 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.
SEF174Y
PBIB1672E
PBIB2636E

DTC P0137, P0157 HO2S2EC-263
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Revision: November 2009 2006 QX56

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-II
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 0.58V at least once during this
procedure.
If the voltage is above 0.58V 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.
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.
Removal and InstallationUBS00H8J
HEATED OXYGEN SENSOR 2
Refer to EM-21, "EXHAUST MANIFOLD AND THREE WAY CATALYST" .
PBIB2054E

EC-264Revision: November 2009
DTC P0138, P0158 HO2S2
2006 QX56
DTC P0138, P0158 HO2S2PFP:226A0
Component DescriptionUBS00N6Y
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.
CONSULT-II Reference Value in Data Monitor ModeUBS00N6Z
Specification data are reference values.
On Board Diagnosis LogicUBS00N70
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 the various driving con-
dition 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 the
various driving condition such as fuel-cut.
SEF327R
MONITOR ITEMCONDITIONSPECIFICATION
HO2S2 (B1)
HO2S2 (B2)

Revving engine from idle to 3,000 rpm quickly 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 - 0.3V
←→ Approx. 0.6 -
1.0V
HO2S2 MNTR (B1)
HO2S2 MNTR (B2) LEAN
←→ RICH
PBIB1848E
PBIB2376E

DTC P0138, P0158 HO2S2EC-265
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Revision: November 2009 2006 QX56
DTC Confirmation ProcedureUBS00N71
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-II
1. Turn ignition switch ON and select “DATA MONITOR” mode with
CONSULT-II.
2. Start engine and warm it up to the normal operating tempera- ture.
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 2 minutes.
6. If 1st trip DTC is detected, go to EC-270, "
PROCEDURE FOR
MALFUNCTION A" .
With GST
Follow the procedure “With CONSULT-II” above.
PROCEDURE FOR MALFUNCTION B
With CONSULT-II
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-II.
2. Start engine and warm it up to the normal operating tempera- ture.
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 to 70 °C (158 °F).
7. Open engine hood.
8. Select “HO2S2 (B1) P1146 ” (for DTC P0138) or “HO2S2 (B2) P1166” (for DTC P0158) of “HO2S2 ” in
“DTC WORK SUPPORT ” mode with CONSULT-II.
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0138
0138
(Bank 1)
Heated oxygen sensor
2 circuit high voltage 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
P0158
0158
(Bank 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
SEF174Y
SEF174Y

EC-266Revision: November 2009
DTC P0138, P0158 HO2S2
2006 QX56
9. Start engine and following the instruction of CONSULT-II.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-272, "
PROCEDURE FOR MALFUNCTION B" .
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 CheckUBS00N72
PROCEDURE FOR MALFUNCTION B
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. 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 (B2) signal] or 74 [HO2S2 (B1) 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 below 0.18V at least once during this
procedure.
If the voltage can be confirmed in step 6, step 7 is not nec-
essary.
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.
The voltage should be below 0.18V at least once during this
procedure.
8. If NG, go to EC-272, "
PROCEDURE FOR MALFUNCTION B" .
PBIB2372E
PBIB2054E