P0140
COMPONENT DESCRIPTION
The rear heated oxygen sensor, after three way catalyst, monitors the oxygen level in the exhaust gas on each bank.
Even it 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.
Terminals 56 Thru 57:
ECM TERMINALS AND REFERENCE VALUE
Specification data are reference values and are measured between each terminal and 32 (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 voltage is unusually high during the various driving condition such as fuel-cut.
DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE
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 5 seconds before conducting the next test.
With Consult
1. Turn ignition switch "ON" and select "DATA MONITOR" mode with CONSULT.
2. Start engine and drive vehicle at a speed of more than 70 KPH (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.
6. If 1st trip DTC is detected, go to "Diagnostic Procedure".
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 terminal 56 (right bank sensor signal) or 57 (left bank sensor 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 2 V during this procedure.
5. If NG, go to "Diagnostic Procedure".
WIRING DIAGRAM
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 0.56 V at least once when the "FUEL INJECTION" is +25%.
- "RR O2 SEN-B1 (-B2)" should be below 0.54 V at least once when the "FUEL INJECTION" is -25%.
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 terminal 56 (right bank sensor signal) or 57 (left bank sensor 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 above 0.56 V at least once during this procedure.
If the voltage is above 0.56 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 0.54 V 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.