P0157
COMPONENT DESCRIPTION
The rear heated oxygen sensor (Rear HO2S), after three way catalyst, monitors the oxygen level in the exhaust gas on each bank.
Even if switching characteristics of the front heated oxygen sensor are shifted, the air fuel ratio is controlled to stoichiometric, by the signal from the rear heated oxygen sensor.
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 rear heated oxygen sensor is not used for engine control operation.
CONSULT REFERENCE VALUE IN DATA MONITOR MODE
Specification data are reference values.
ECM TERMINALS AND REFERENCE VALUE
Specification data are reference values, and are measured between each terminal and (25) (ECM ground).
ON BOARD DIAGNOSIS LOGIC
The rear heated oxygen sensor has a much longer switching time between rich and lean than the front heated oxygen sensor. The oxygen storage capacity before the three way catalyst causes the longer switching time. To judge the malfunctions of rear heated oxygen sensor, ECM monitors whether the minimum voltage of the sensor is sufficiently low during the various driving condition such as fuel-cut.
DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE
CAUTION: Always drive vehicle at a safe speed.
NOTE:
- "COMPLETED" will appear on CONSULT screen when all tests "COND1", "COND2" and "COND3" are completed.
- If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF" and wait at least 10 seconds before conducting the next test.
TESTING CONDITION: Never stop engine during this test. If the engine is stopped, reperform this test from step 2.
Procedure for COND1
With Consult
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" and select "RR O2 SEN-B1 (-B2) P0137 (P0157)" of "REAR O2 SENSOR" in "DTC WORK SUPPORT" mode with CONSULT
4. Touch "START".
5. Start engine and let it idle for at least 30 seconds.
6. Rev engine up to 2,000 rpm 2 or 3 times quickly under no load.
If "COMPLETED" appears on CONSULT screen, go to step 10.
If "COMPLETED" does not appear on CONSULT screen, go to the following step.
7. Drive vehicle at a speed of more than 70 KPH (43 MPH) for 2 consecutive minutes.
8. When the following conditions are met, "TESTING" will be displayed at "COND1" on the CONSULT screen. Maintain the conditions continuously until "TESTING" changes to "COMPLETED". (It will take approximately 60 seconds.)
CKPS.RPM (POS): 1,400 - 2,800 rpm (A/T models) 1,400 - 3,100 rpm (M/T models)
Vehicle speed: 64 - 120 KPH (40 - 75 MPH)
B/FUEL SCHDL: 0.5 - 5.0 msec
Selector lever: Suitable position
NOTE:
- If "TESTING" is not displayed after 5 minutes, retry from step 2.
- If "COMPLETED" already appears at "COND2" on CONSULT screen before "Procedure for COND2" is conducted, it is unnecessary to conduct step 9.
Procedure for COND2
8. While driving release accelerator pedal completely with "OD" OFF (A/T models only) from the above condition (step 7) until "INCOMPLETE" at "COND2" on CONSULT screen has turned to "COMPLETED". (It will take approximately 4 seconds.)
NOTE: If "COMPLETED" already appears at "COND3" on CONSULT screen before "Procedure for COND3" is conducted, it is unnecessary to conduct step 9.
Procedure for COND3
10. Stop vehicle and let it idle until "INCOMPLETE" of "COND3" on CONSULT screen has turned to "COMPLETED". (It will take a maximum of approximately 6 minutes.)
11. Make sure that "OK" is displayed after touching "SELF DIAG RESULTS". If "NG" is displayed, refer to "DIAGNOSTIC PROCEDURE".
OR
OVERALL FUNCTION CHECK
Use this procedure to check the overall function of the rear heated oxygen sensor circuit. During this check, a 1st trip DTC might not be confirmed.
Without Consult
1. Start engine and drive vehicle at a speed of more than 70 KPH (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminals (56) (RH),(57) (LH) (sensor signal) and ground.
4. Check the voltage when revving engine 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 0.43 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 KPH (50 MPH) in 3rd gear position (M/T), D position with "OD" OFF (A/T).
The voltage should be below 0.43 V at least once during this procedure.
6. If NG, go to "DIAGNOSTIC PROCEDURE".
WIRING DIAGRAM
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DIAGNOSTIC PROCEDURE
COMPONENT INSPECTION
With Consult
1. Start engine and drive vehicle at a speed of more than 70 KPH (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Select "FUEL INJECTION" in "ACTIVE TEST" mode and select "RR O2 SEN-B1 (-B2)" as the monitor item with CONSULT.
4. Check "RR O2 SEN-B1 (-B2)" at idle speed when adjusting "FUEL INJECTION" to ± 25%.
"RR O2 SEN-B1 (-B2)" should be above 0.48 V at least once when the "FUEL INJECTION" is +25%. "RR O2 SEN-B1 (-B2)" should be below 0.43 V at least once when the "FUEL INJECTION" is -25%.
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.
OR
Without Consult
1. Start engine and drive vehicle at a speed of more than 70 KPH (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminals (56) (RH),(57) (LH) (sensor signal) and 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 above 0.48 V at least once. If the voltage is above 0.48 V at 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 KPH (50 MPH) in 3rd gear position (M/T), D position with "OD" OFF (A/T).
The voltage should be below 0.43 V at least once.
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.