P0137

COMPONENT DESCRIPTION
The heated oxygen sensor 2 (rear), after three way catalyst (Manifold), monitors 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 1 V in richer conditions to 0 V 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:

ON BOARD DIAGNOSIS LOGIC
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 (Manifold) causes the longer switching time. To judge the malfunctions of heated oxygen sensor 2 (rear), ECM monitors whether the minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut.

Malfunction is detected when the minimum voltage from the sensor is not reached to the specified voltage.

Possible Cause
- Harness or connectors (The sensor circuit is open or shorted.)
- Heated oxygen sensor 2 (rear)
- Fuel pressure
- Injectors

DTC Confirmation Procedure

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
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Turn ignition switch "ON".
4. Select "DATA MONITOR" mode with CONSULT-II.
5. Make sure that "COOLAN TEMP/S" indicates more than 70 °C (158 °F).

6. Select "HO2S2 (B1) P0137" or "HO2S2 (B2) P0157" of "HO2S2" in "DTC WORK SUPPORT" mode with CONSULT-II.
7. Start engine and follow the instruction of CONSULT-II.

8. Make sure that "OK" is displayed after touching "SELF-DIAG RESULTS".
If NG is displayed, refer to "Diagnostic Procedure" at the end of the article.
If "CANNOT BE DIAGNOSED" is displayed, perform the following.
a. Stop engine and cool down until "COOLAN TEMP/S" indicates less than 70 °C (158 °F).
b. Turn ignition switch "ON".
c. Select "DATA MONITOR" mode with CONSULT-II.
d. Start engine.
e. Return to step 6 again when the "COOLAN TEMP/S" reaches to 70 °C (158 °F).

Overall Function Check
Use this procedure to check the overall function of the heated oxygen sensor 2 (rear) circuit. During this check, a 1st trip DTC might not be confirmed.

WITH GST
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 (B1) signal] or 71 [HO2S2 (B2) 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 0.54 V 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 3rd gear position (M/T), "D" position with "OD" OFF (A/T).
The voltage should be below 0.54 V at least once during this procedure.
6. If NG, go to "Diagnostic Procedure" below.