P0140

Component Description
The rear heated oxygen sensor (Rear HO2S), after three way catalyst, monitors the oxygen level in the exhaust gas.

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-II 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 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 or not the voltage is too high during various driving conditions such as fuel-cut.

DTC Confirmation Procedure

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-II
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. Maintain the following conditions for at least 5 consecutive seconds.

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-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (4 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.




3. Set voltmeter probes between ECM terminals 56 (Rear heated oxygen sensor signal) and ECM ground.
4. Check the voltage after revving 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" below.

EC-RRO2-01:

Wiring Diagram

Step 1 - 3:

Step 4 - 5:

Step 6:

Step 7 - 8:

Step 9 - 10:

Diagnostic Procedure