P0136

The rear heated oxygen sensor is placed into the front exhaust tube. It detects the amount of oxygen in the exhaust gas compared to the outside air. The rear heated oxygen sensor has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The rear heated oxygen sensor signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air- fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.
Under normal conditions the rear heated oxygen sensor is not used for engine control operation.




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 of the three way catalyst causes the longer-switching time. To judge the malfunctions of rear heated oxygen sensor, ECM monitors the sensor's voltage value and the switching response during the various driving condition such as fuel-cut.

OVERALL FUNCTION CHECK
Use this procedure to check the overall function of the mar heated oxygen sensor circuit. During this check, a 1st trip DTC might not be confirmed.

With Consult
(1) Start engine and warm it up sufficiently.




(2) Select "FUEL INJECTION" in "ACTIVE TEST" mode, and select "RR O2 SENSOR" as the monitor item with CONSULT.
(3) Check "RR O2 SENSOR" at idle speed when adjusting "FUEL INJECTION" to ±25%.
"RR O2 SENSOR" should be above 0.60V at least once when the "FUEL INJECTION" is +25%. "RR O2 SENSOR" should be below 0.55V at least once when the "FUEL INJECTION" is -25%.

OR

Without Consult
(1) Start engine and warm it up sufficiently.




(2) Set voltmeter probes between ECM terminal (52) (sensor signal) and (43) (engine ground).
(3) 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 above 0.6V at least once. If the voltage is above 0.6V at step 3, step 4 is not necessary.
(4) Check the voltage when revving engine up to 6,000 rpm under no load or 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 The voltage should be above 0.48V and below 0.43V at least once during this procedure.

EC-RRO2-01 Rear Heated Oxygen Sensor (Rear HO2S) (DTC P0136):

WIRING DIAGRAM




DIAGNOSTIC PROCEDURE