2001 INFINITI QX4 02 sensor

9 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
DTC P0139, P0159 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(RESPONSE MONITORING)
Diagnostic Procedure (Cont'd)
EC-276

SEF327R
Component DescriptionNBEC0154The 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
NBEC0155Specification 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 ValueNBEC0661Specification 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
SEF305UA
On Board Diagnosis LogicNBEC0157The 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 voltage
is unusually high during the various driving condition such as fuel-
cut.
Malfunction is detected when an excessively high voltage from the
sensor is sent to ECM.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Component Description
EC-277

Possible CauseNBEC0441IHarness or connectors
(The sensor circuit is open or shorted.)
IHeated oxygen sensor 2 (rear)
SEF189Y
DTC Confirmation ProcedureNBEC0158CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-IINBEC0158S011) Turn ignition switch ªONº and select ªDATA MONITORº mode
with CONSULT-II.
2) Start engine and drive vehicle at a speed of more than 70 km/h
(43 MPH) for 2 consecutive minutes.
3) Stop vehicle with engine running.
4) Let engine idle for 1 minute.
5) Maintain the following conditions for at least 5 consecutive
seconds.
ENG SPEED 1,300 - 3,100 rpm
VHCL SPEED SE 64 - 130 km/h (40 - 80 MPH)
B/FUEL SCHDL 0.5 - 6.4 msec
COOLAN TEMP/S More than 70ÉC (158ÉF)
Selector lever Suitable position
6) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-282.
SEF312XB
Overall Function CheckNBEC0159Use 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 GSTNBEC0159S011) 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 P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Possible Cause
EC-278

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 1.4V during this procedure.
5) If NG, go to ªDiagnostic Procedureº, EC-282.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Overall Function Check (Cont'd)
EC-279

Wiring DiagramNBEC0160RIGHT BANKNBEC0160S01
MEC951C
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Wiring Diagram
EC-280

LEFT BANKNBEC0160S02
MEC952C
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Wiring Diagram (Cont'd)
EC-281

Diagnostic ProcedureNBEC0161
1 INSPECTION START
1. Turn ignition switch ªOFFº.
2. Loosen and retighten engine ground screws.
SEF959Y
3. Check heated oxygen sensor 2 (rear) harness protector color.
SEF372Z
4. Disconnect corresponding heated oxygen sensor 2 (rear) harness connector.
SEF971Y
5. Disconnect ECM harness connector.
©GO TO 2.
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure
EC-282

2 CHECK HO2S2 (REAR) INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between ECM terminal and HO2S2 terminal as follows.
Refer to Wiring Diagram.
MTBL0527
Continuity should exist.
2. Check harness continuity between ECM terminal or HO2S2 terminal and ground as follows.
Refer to Wiring Diagram.
MTBL0528
Continuity should not exist.
3. Also check harness for 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 (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©GO TO 4.
NG©Repair open circuit or short to power in harness or connectors.
4 CHECK HO2S2 (REAR) CONNECTORS FOR WATER
Check heated oxygen sensor connector 2 (rear) and harness connector for water.
Water should not exist.
OK or NG
OK (With CONSULT-II)©GO TO 5.
OK (Without CONSULT-
II)©GO TO 6.
NG©Repair or replace harness or connectors.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure (Cont'd)
EC-283