Infiniti QX4 (R50). Manual - part 197

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.)

SEF313XA

OK or NG

GO TO 9.

GO TO 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 “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

GO TO 9.

GO TO 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).

IDX

DTC P0137, P0157 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)

(MIN. VOLTAGE MONITORING)

Diagnostic Procedure (Cont’d)

EC-255

CHECK INTERMITTENT INCIDENT

Refer to “TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT”, 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 Description

NBEC0138

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

NBEC0139

Specification data are reference values.

MONITOR ITEM

CONDITION

SPECIFICATION

HO2S2 (B1)
HO2S2 (B2)

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

NBEC0659

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)

Heated oxygen sensor
2 (rear) (bank 1)

[Engine is running]

Warm-up condition

Engine speed is 2,000 rpm.

0 - Approximately 1.0V

OR/L

Heated oxygen sensor
2 (rear) (bank 2)

[Engine is running]

Warm-up condition

Engine speed is 2,000 rpm.

0 - Approximately 1.0V

SEF303UB

On Board Diagnosis Logic

NBEC0141

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 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.

IDX

DTC P0138, P0158 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)

(MAX. VOLTAGE MONITORING)

Component Description

EC-257

Possible Cause

NBEC0439

Harness or connectors
(The sensor circuit is open or shorted.)

Heated oxygen sensor 2 (rear)

Fuel pressure

Injectors

Intake air leaks

SEF663Y

SEF664Y

SEF665Y

DTC Confirmation Procedure

NBEC0142

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.
TESTING CONDITION:
Open engine hood before conducting following procedure.

WITH CONSULT-II

NBEC0142S01

Start engine and warm it up to normal operating temperature.

Turn ignition switch “OFF” and wait at least 10 seconds.

Turn ignition switch “ON”.

Select “DATA MONITOR” mode with CONSULT-II.

Make sure that “COOLAN TEMP/S” indicates more than 70°C
(158°F).

Select “HO2S2 (B1)/(B2) P0138/P0158” of “HO2S2” in “DTC
WORK SUPPORT” mode with CONSULT-II.

Start engine and follow the instruction of CONSULT-II.

Make sure that “OK” is displayed after touching “SELF-DIAG
RESULTS”.
If NG is displayed, refer to “Diagnostic Procedure”, EC-262.
If “CANNOT BE DIAGNOSED” is displayed, perform the fol-
lowing.

Stop engine and cool down until “COOLAN TEMP/S” indicates
less than 70°C (158°F).

Turn ignition switch “ON”.

Select “DATA MONITOR” mode with CONSULT-II.

Start engine.

Return to step 6 again when the “COOLAN TEMP/S” reaches
to 70°C (158°F).

SEF312XB

Overall Function Check

NBEC0143

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

NBEC0143S01

Start engine and drive vehicle at a speed of more than 70 km/h
(43 MPH) for 2 consecutive minutes.

Stop vehicle with engine running.

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

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