2001 INFINITI QX4 02 sensor

Diagnostic ProcedureNBEC0137
1 RETIGHTEN GROUND SCREWS
1. Turn ignition switch ªOFFº.
2. Loosen and retighten engine ground screws.
SEF959Y
©GO TO 2.
2 CLEAR THE SELF-LEARNING DATA
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Select ªSELF-LEARNING CONTº in ªWORK SUPPORTº mode with CONSULT-II.
3. Clear the self-learning control coefficient by touching ªCLEARº.
SEF968Y
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-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch ªOFFº.
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 connector.
5. Make sure 1st trip DTC P0100 is displayed.
6. Erase the 1st trip DTC memory. Refer to ªHOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATIONº,
EC-72.
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?
YesorNo
Ye s©Perform trouble diagnosis for DTC P0172, P0175. Refer to EC-302.
No©GO TO 3.
DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Diagnostic Procedure
EC-252

3 CHECK HO2S2 (REAR) INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Check heated oxygen sensor 2 (rear) harness protector color.
SEF372Z
3. Disconnect corresponding heated oxygen sensor 2 (rear) harness connector.
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4. Disconnect ECM harness connector.
5. Check harness continuity between ECM terminal and rear HO2S terminal as follows.
Refer to Wiring Diagram.
MTBL0521
Continuity should exist.
6. Check harness continuity between ECM terminal or HO2S2 terminal and ground as follows.
Refer to Wiring Diagram.
MTBL0522
Continuity should not exist.
7. 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.
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DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Diagnostic Procedure (Cont'd)
EC-253

4 CHECK HO2S2 (REAR) GROUND CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between HO2S2 terminal 4 and engine ground.
Refer to Wiring Diagram.
Continuity should exist.
2. Also check harness for short to power.
OK or NG
OK (With CONSULT-II)©GO TO 5.
OK (Without CONSULT-
II)©GO TO 6.
NG©Repair open circuit or short to power in harness or connectors.
5 CHECK HEATED OXYGEN SENSOR 2 (REAR)
With CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Select ªFUEL INJECTIONº in ªACTIVE TESTº mode, and select ªHO2S2 (B1)/(B2)º as the monitor item with CONSULT-
II.
4. Check ªHO2S2 (B1)/(B2)º at idle speed when adjusting ªFUEL INJECTIONº to±25%.
SEF972Y
ªHO2S2 (B1)/(B2)º should be above 0.62V at least once when the ªFUEL INJECTIONº is +25%.
ªHO2S2 (B1)/(B2)º should be below 0.57V at least once when the ªFUEL INJECTIONº is þ25%.
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.
OK or NG
OK©GO TO 9.
NG©GO TO 8.
DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Diagnostic Procedure (Cont'd)
EC-254

6 CHECK HEATED OXYGEN SENSOR 2 (REAR)-I
Without CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminal 72 (HO2S2 bank 1 right signal) or 71 (HO2S2 bank 2 left signal) and
engine ground.
4. Check the voltage when rewing up to 4,000 rpm under no load at least 10 times.
(Depress and release accelerator pedal as soon as possible.)
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OK or NG
OK©GO TO 9.
NG©GO TO 7.
7 CHECK HEATED OXYGEN SENSOR 2 (REAR)-II
Idle vehicle for 10 minutes, then check voltage between the same terminals as in Test No. 6; or check voltage when coast-
ing from 80 km/h (50 MPH) in ªDº position with ªODº OFF.
The voltage should go below 0.57V at least once during this procedure.
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.
OK or NG
OK©GO TO 9.
NG©GO TO 8.
8 REPLACE HEATED OXYGEN SENSOR 2 (REAR)
1. Stop vehicle and turn ignitioin switch OFF.
2. Check heated oxygen sensor 2 (rear) harness protector color.
SEF372Z
CAUTION:
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.
©Replace malfunctioning heated oxygen sensor 2 (rear).
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DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Diagnostic Procedure (Cont'd)
EC-255

9 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Diagnostic Procedure (Cont'd)
EC-256

SEF327R
Component DescriptionNBEC0138The heated oxygen sensor 2 (rear), after three way catalyst, moni-
tors the oxygen level in the exhaust gas on each bank.
Even if switching characteristics of the heated oxygen sensor 1
(front) are shifted, the air fuel ratio is controlled to stoichiometric,
by the signal from the heated oxygen sensor 2 (rear).
This sensor is made of ceramic zirconia. The zirconia generates
voltage from approximately 1V in richer conditions to 0V in leaner
conditions.
Under normal conditions the heated oxygen sensor 2 (rear) is not
used for engine control operation.
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0139Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
HO2S2 (B1)
HO2S2 (B2)
IEngine: After warming upRevving engine from idle up to
2,000 rpm0 - 0.3V+,Approx. 0.6 - 1.0V
HO2S2 MNTR
(B1)
HO2S2 MNTR
(B2)LEAN+,RICH
ECM Terminals and Reference ValueNBEC0659Specification 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.
TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
72 ORHeated oxygen sensor
2 (rear) (bank 1)[Engine is running]
IWarm-up condition
IEngine speed is 2,000 rpm.0 - Approximately 1.0V
71 OR/LHeated oxygen sensor
2 (rear) (bank 2)[Engine is running]
IWarm-up condition
IEngine speed is 2,000 rpm.0 - Approximately 1.0V
SEF303UB
On Board Diagnosis LogicNBEC0141The heated oxygen sensor 2 (rear) has a much longer switching
time between rich and lean than the heated oxygen sensor 1
(front). The oxygen storage capacity before the three way catalyst
causes the longer switching time. To judge the malfunctions of
heated oxygen sensor 2 (rear), ECM monitors whether the maxi-
mum voltage of the sensor is sufficiently high during the various
driving condition such as fuel-cut.
Malfunction is detected when the maximum voltage from the sen-
sor is not reached to the specified voltage.
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DTC P0138, P0158 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MAX. VOLTAGE MONITORING)
Component Description
EC-257

Possible CauseNBEC0439IHarness or connectors
(The sensor circuit is open or shorted.)
IHeated oxygen sensor 2 (rear)
IFuel pressure
IInjectors
IIntake air leaks
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SEF664Y
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DTC Confirmation ProcedureNBEC0142NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
TESTING CONDITION:
Open engine hood before conducting following procedure.
WITH CONSULT-IINBEC0142S011) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Turn ignition switch ªONº.
4) Select ªDATA MONITORº mode with CONSULT-II.
5) Make sure that ªCOOLAN TEMP/Sº indicates more than 70ÉC
(158ÉF).
6) Select ªHO2S2 (B1)/(B2) P0138/P0158º of ªHO2S2º in ªDTC
WORK SUPPORTº mode with CONSULT-II.
7) Start engine and follow the instruction of CONSULT-II.
8) Make sure that ªOKº is displayed after touching ªSELF-DIAG
RESULTSº.
If NG is displayed, refer to ªDiagnostic Procedureº, EC-262.
If ªCANNOT BE DIAGNOSEDº is displayed, perform the fol-
lowing.
a) Stop engine and cool down until ªCOOLAN TEMP/Sº indicates
less than 70ÉC (158ÉF).
b) Turn ignition switch ªONº.
c) Select ªDATA MONITORº mode with CONSULT-II.
d) Start engine.
e) Return to step 6 again when the ªCOOLAN TEMP/Sº reaches
to 70ÉC (158ÉF).
SEF312XB
Overall Function CheckNBEC0143Use this procedure to check the overall function of the heated oxy-
gen sensor 2 (rear) circuit. During this check, a 1st trip DTC might
not be confirmed.
WITH GSTNBEC0143S011) Start engine and drive vehicle at a speed of more than 70 km/h
(43 MPH) for 2 consecutive minutes.
2) Stop vehicle with engine running.
3) Set voltmeter probes between ECM terminal 72 (HO2S2 bank
DTC P0138, P0158 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MAX. VOLTAGE MONITORING)
Possible Cause
EC-258

1 right signal) or 71 (HO2S2 bank 2 left signal) and engine
ground.
4) Check the voltage when racing 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 0.62V at least once during
this procedure.
If the voltage can be confirmed in step 4, step 5 is not
necessary.
5) Keep vehicle at idling for 10 minutes, then check the voltage.
Or check the voltage when coasting from 80 km/h (50 MPH)
in ªDº position with ªODº OFF.
The voltage should be above 0.62V at least once during
this procedure.
6) If NG, go to ªDiagnostic Procedureº, EC-262.
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DTC P0138, P0158 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MAX. VOLTAGE MONITORING)
Overall Function Check (Cont'd)
EC-259