INFINITI QX56 2007 Factory Service Manual

EC-268
< SERVICE INFORMATION >
DTC P0137, P0157 HO2S2
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.
• 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.
PBIB1672E
PBIB2636E
PBIB2054E

DTC P0137, P0157 HO2S2
EC-269
< SERVICE INFORMATION >
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Removal and InstallationINFOID:0000000003531773
HEATED OXYGEN SENSOR 2
Refer to EM-21 .

EC-270
< SERVICE INFORMATION >
DTC P0138, P0158 HO2S2
DTC P0138, P0158 HO2S2
Component DescriptionINFOID:0000000003531774
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 ModeINFOID:0000000003531775
Specification data are reference values.
On Board Diagnosis LogicINFOID:0000000003531776
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 ITEM CONDITION SPECIFICATION
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 load0 - 0.3V ←→ Approx. 0.6 -
1.0V
HO2S2 MNTR (B1)
HO2S2 MNTR (B2)LEAN ←→ RICH
PBIB1848E
PBIB2376E

DTC P0138, P0158 HO2S2
EC-271
< SERVICE INFORMATION >
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DTC Confirmation ProcedureINFOID:0000000003531777
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-276, "
Diagnosis Procedure".
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 voltageA)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-272
< SERVICE INFORMATION >
DTC P0138, P0158 HO2S2
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-276, "
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 CheckINFOID:0000000003531778
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-276, "
Diagnosis Procedure".
PBIB2372E
PBIB2054E

DTC P0138, P0158 HO2S2
EC-273
< SERVICE INFORMATION >
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Wiring DiagramINFOID:0000000003531779
BANK 1
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.
BBWA2800E

EC-274
< SERVICE INFORMATION >
DTC P0138, P0158 HO2S2
TER-
MI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
6GRHeated oxygen sensor 2
heater (bank 1)[Engine is running]
• Engine speed: Below 3,600 rpm after the fol-
lowing 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 load0 - 1.0V
[Ignition switch: ON]
• Engine: Stopped
[Engine is running]
• Engine speed: Above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)
55 RHeated oxygen sensor 2
(bank 1)[Engine is running]
• Revving engine from idle to 3,000 rpm quick-
ly 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 load0 - Approximately 1.0V
78 B/WSensor ground
(Heated oxygen sensor 2) [Engine is running]
•Warm-up condition
• Idle speed Approximately 0V

DTC P0138, P0158 HO2S2
EC-275
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BANK 2
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.
BBWA2801E

EC-276
< SERVICE INFORMATION >
DTC P0138, P0158 HO2S2
Diagnosis Procedure
INFOID:0000000003531780
PROCEDURE FOR MALFUNCTION A
1.CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten two ground screws on the body.
Refer to EC-143, "
Ground Inspection".
OK or NG
OK >> GO TO 2.
NG >> Repair or replace ground connections.
2.CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT
TER-
MI-
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NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
25 O/GHeated oxygen sensor 2
heater (bank 2)[Engine is running]
• Engine speed: Below 3,600 rpm after the fol-
lowing 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 load0 - 1.0V
[Ignition switch: ON]
• Engine: Stopped
[Engine is running]
• Engine speed: Above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)
74 LHeated oxygen sensor 2
(bank 2)[Engine is running]
• Revving engine from idle to 3,000 rpm quick-
ly 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 load0 - Approximately 1.0V
78 B/WSensor ground
(Heated oxygen sensor 2) [Engine is running]
•Warm-up condition
• Idle speed Approximately 0V
BBIA0354E

DTC P0138, P0158 HO2S2
EC-277
< SERVICE INFORMATION >
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1. Disconnect heated oxygen sensor 2 harness connector.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminal 78 and HO2S2 terminal 4.
Refer to Wiring Diagram.
4. Also check harness for short to ground and short to power.
OK or NG
OK >> GO TO 3.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
3.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 4.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.
4.CHECK HO2S2 CONNECTOR FOR WATER
Check connectors for water.
OK or NG
OK >> GO TO 5.
NG >> Repair or replace harness or connectors.
5.CHECK HEATED OXYGEN SENSOR 2Continuity should exist.
BBIA0435E
DTCTe r m i n a l s
Bank
ECM Sensor
P0138 55 1 1
P0158 74 1 2
Continuity should exist.
DTCTe r m i n a l s
Bank
ECM Sensor
P0138 55 1 1
P0158 74 1 2
Continuity should not exist.
Water should not exist.