2001 INFINITI QX4 engine

5) Restart engine and let it idle for 25 seconds.
6) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-236.
WITH GSTNBEC0120S021) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Restart engine and let it idle for 25 seconds.
4) Turn ignition switch ªOFFº and wait at least 10 seconds.
5) Restart engine and let it idle for 25 seconds.
6) Select ªMODE 3º with GST.
7) If DTC is detected, go to ªDiagnostic Procedureº, EC-236.
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 P0134, P0154 HEATED OXYGEN SENSOR 1 (FRONT) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
DTC Confirmation Procedure (Cont'd)
EC-233

5 CHECK HEATED OXYGEN SENSOR 1 (FRONT)
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Select ªMANU TRIGº and adjust ªTRIGGER POINTº to 100% in ªDATA MONITORº mode with CONSULT-II.
3. Select ªHO2S1 (B1)/(B2)º and ªHO2S1 MNTR (B1)/(B2)º.
4. Hold engine speed at 2,000 rpm under no load during the following steps.
5. Touch ªRECORDº on CONSULT-II screen.
SEF967Y
6. Check the following.
IªHO2S1 MNTR (B1)/(B2)º in ªDATA MONITORº mode changes from ªRICHº to ªLEANº to ªRICHº 5 times in 10 seconds.
5 times (cycles) are counted as shown left:
SEF647Y
IªHO2S1 (B1)/(B2)º voltage goes above 0.6V at least once.
IªHO2S1 (B1)/(B2)º voltage goes below 0.3V at least once.
IªHO2S1 (B1)/(B2)º voltage never exceeds 1.0V.
SEF648Y
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 8.
NG©GO TO 7.
DTC P0134, P0154 HEATED OXYGEN SENSOR 1 (FRONT) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure (Cont'd)
EC-238

6 CHECK HEATED OXYGEN SENSOR 1 (FRONT)
Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Set voltmeter probes between ECM terminal 63 (HO2S1 bank 1 right signal) or 62 (HO2S1 bank 2 left signal) and
engine ground.
3. Check the following with engine speed held at 2,000 rpm constant under no load.
SEF967XA
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 8.
NG©GO TO 7.
7 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).
8 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
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DTC P0134, P0154 HEATED OXYGEN SENSOR 1 (FRONT) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure (Cont'd)
EC-239

DescriptionNBEC0123SYSTEM DESCRIPTIONNBEC0123S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS)
Engine speedHeated
oxygen
sensor 1
heater
(front) con-
trolHeated oxygen sensor 1 heat-
ers (front)
Crankshaft position sensor (REF)
The ECM performs ON/OFF control of the heated oxygen sensor 1 heaters (front) corresponding to the engine
speed.
OPERATIONNBEC0123S02
Engine speed rpm Heated oxygen sensor 1 heaters (front)
Above 3,600 OFF
Below 3,600 ON
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0124Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
HO2S1 HTR (B1)
HO2S1 HTR (B2)IEngine speed: Below 3,600 rpm ON
IEngine speed: Above 3,600 rpm OFF
ECM Terminals and Reference ValueNBEC0657Specification 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)
3 L/ORHeated oxygen sensor
1 heater (front) (bank
1)[Engine is running]
IEngine speed is below 3,600 rpm.0 - 1.0V
[Engine is running]
IEngine speed is above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)
2 R/GHeated oxygen sensor
1 heater (front) (bank
2)[Engine is running]
IEngine speed is below 3,600 rpm.0 - 1.0V
[Engine is running]
IEngine speed is above 3,600 rpm.BATTERY VOLTAGE
(11 - 14V)
DTC P0135, P0155 HEATED OXYGEN SENSOR 1 HEATER (FRONT) (BANK
1)/(BANK 2)
Description
EC-240

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

SEF327R
Component DescriptionNBEC0130The 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
NBEC0131Specification 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 ValueNBEC0658Specification 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
SEF304UB
On Board Diagnosis LogicNBEC0133The 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 mini-
mum voltage of sensor is sufficiently low during the various driving
condition such as fuel-cut.
Malfunction is detected when the minimum voltage from the sen-
sor is not reached to the specified voltage.
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DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Component Description
EC-247

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

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 below 0.57V 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 below 0.57V at least once during
this procedure.
6) If NG, go to ªDiagnostic Procedureº, EC-252.
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DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(MIN. VOLTAGE MONITORING)
Overall Function Check (Cont'd)
EC-249