Infiniti QX4 (R50). Manual — part 202
6
CHECK REAR 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 revving up to 4,000 rpm under no load at least 10 times.
(Depress and release accelerator pedal as soon as possible.)
SEF313XA
OK or NG
OK
©
GO TO 9.
NG
©
GO TO 7.
7
CHECK REAR 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 “D” position with “OD” 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 REAR HEATED OXYGEN SENSOR
1. Stop vehicle and turn ignition 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).
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0139, P0159 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(RESPONSE MONITORING)
Diagnostic Procedure (Cont’d)
EC-275
9
CHECK INTERMITTENT INCIDENT
Refer to “TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT”, 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 Description
NBEC0154
The 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
NBEC0155
Specification data are reference values.
MONITOR ITEM
CONDITION
SPECIFICATION
HO2S2 (B1)
HO2S2 (B2)
I
Engine: After warming up
Revving engine from idle up to
2,000 rpm
0 - 0.3V
+,
Approx. 0.6 - 1.0V
HO2S2 MNTR
(B1)
HO2S2 MNTR
(B2)
LEAN
+,
RICH
ECM Terminals and Reference Value
NBEC0661
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.
TERMI-
NAL
NO.
WIRE
COLOR
ITEM
CONDITION
DATA (DC Voltage)
72
OR
Heated oxygen sensor
2 (rear) (bank 1)
[Engine is running]
I
Warm-up condition
I
Engine speed is 2,000 rpm.
0 - Approximately 1.0V
71
OR/L
Heated oxygen sensor
2 (rear) (bank 2)
[Engine is running]
I
Warm-up condition
I
Engine speed is 2,000 rpm.
0 - Approximately 1.0V
SEF305UA
On Board Diagnosis Logic
NBEC0157
The 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 Cause
NBEC0441
I
Harness or connectors
(The sensor circuit is open or shorted.)
I
Heated oxygen sensor 2 (rear)
SEF189Y
DTC Confirmation Procedure
NBEC0158
CAUTION:
Always drive vehicle at a safe speed.
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.
WITH CONSULT-II
NBEC0158S01
1)
Turn ignition switch “ON” and select “DATA MONITOR” 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 70°C (158°F)
Selector lever
Suitable position
6)
If 1st trip DTC is detected, go to “Diagnostic Procedure”,
EC-282.
SEF312XB
Overall Function Check
NBEC0159
Use 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 GST
NBEC0159S01
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
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Possible Cause
EC-278
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