2001 INFINITI QX4 ignition

On Board Diagnosis LogicNBEC0126Malfunction is detected when the current amperage in the heated
oxygen sensor 1 heater (front) circuit is out of the normal range.
[An improper voltage drop signal is sent to ECM through the heated
oxygen sensor 1 heater (front).]
Possible CauseNBEC0437IHarness or connectors
(The heated oxygen sensor 1 heater (front) circuit is open or
shorted.)
IHeated oxygen sensor 1 heater (front)
SEF058Y
DTC Confirmation ProcedureNBEC0127NOTE:
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:
Before performing the following procedure, confirm that bat-
tery voltage is between 10.5V and 16V at idle.
WITH CONSULT-IINBEC0127S011) Turn ignition switch ªONº and select ªDATA MONITORº mode
with CONSULT.
2) Start engine and run it for at least 6 seconds at idle speed.
3) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-244.
WITH GSTNBEC0127S021) Start engine and run it for at least 6 seconds at idle speed.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Start engine and run it for at least 6 seconds at idle speed.
4) Select ªMODE 3º with GST.
5) If DTC is detected, go to ªDiagnostic Procedureº, EC-244.
IWhen using GST, ªDTC Confirmation Procedureº should
be performed twice as much as when using CONSULT-II
because GST cannot display MODE 7 (1st trip DTC) con-
cerning this diagnosis. Therefore, using CONSULT-II is
recommended.
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DTC P0135, P0155 HEATED OXYGEN SENSOR 1 HEATER (FRONT) (BANK
1)/(BANK 2)
On Board Diagnosis Logic
EC-241

Diagnostic ProcedureNBEC0129
1 CHECK HO2S1 (FRONT) POWER SUPPLY CIRCUIT
1. Turn ignition switch ªOFFº.
2. Check heated oxygen sensor 1 (front) harness protector color.
SEF505Y
3. Disconnect corresponding heated oxygen sensor 1 (front) harness connector.
SEF965Y
SEF966Y
4. Turn ignition switch ªONº.
5. Check voltage between HO2S1 (front) terminal 1 and ground with CONSULT-II or tester.
SEF970Y
OK or NG
OK©GO TO 3.
NG©GO TO 2.
DTC P0135, P0155 HEATED OXYGEN SENSOR 1 HEATER (FRONT) (BANK
1)/(BANK 2)
Diagnostic Procedure
EC-244

2 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors M32, F23
IFuse block (J/B) connector M10
I15A fuse
IHarness for open or short between heated oxygen sensor 1 (front) and fuse
©Repair harness or connectors.
3 CHECK HO2S1 (FRONT) OUTPUT CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminal and HO2S1 terminal as follows.
Refer to Wiring Diagram.
MTBL0520
Continuity should exist.
4. 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 HEATED OXYGEN SENSOR 1 HEATER (FRONT)
Check resistance between HO2S1 (front) terminals as follows.
SEF969Y
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 6.
NG©GO TO 5.
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DTC P0135, P0155 HEATED OXYGEN SENSOR 1 HEATER (FRONT) (BANK
1)/(BANK 2)
Diagnostic Procedure (Cont'd)
EC-245

5 REPLACE HEATED OXYGEN SENSOR 1 (FRONT)
1. Turn ignition switch ªOFFº.
2. Check heated oxygen sensor 1 (front) harness protector color.
SEF505Y
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 1 (front).
6 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
DTC P0135, P0155 HEATED OXYGEN SENSOR 1 HEATER (FRONT) (BANK
1)/(BANK 2)
Diagnostic Procedure (Cont'd)
EC-246

Possible CauseNBEC0438IHarness or connectors
(The sensor circuit is open or shorted.)
IHeated oxygen sensor 2 (rear)
IFuel pressure
IInjectors
SEF340Z
SEF341Z
SEF342Z
DTC Confirmation ProcedureNBEC0134NOTE:
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-IINBEC0134S011) 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) P0137/P0157º 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-252.
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 CheckNBEC0135Use 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 GSTNBEC0135S011) 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 P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Possible Cause
EC-248

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.
SEF971Y
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

Possible CauseNBEC0439IHarness or connectors
(The sensor circuit is open or shorted.)
IHeated oxygen sensor 2 (rear)
IFuel pressure
IInjectors
IIntake air leaks
SEF663Y
SEF664Y
SEF665Y
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