Rear Heated Oxygen Sensor

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 the sensor's voltage value and the switching response during the various driving conditions such as fuel-cut.

OVERALL FUNCTION CHECK
Use this procedure to check the overall function of the rear heated oxygen sensor circuit. During this check, a 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 02 SENSOR" at idle speed when adjusting "FUEL INJECTION" to ±25%.

"RR O2 SENSOR" should be above O.48V at least once when the "FUEL INJECTION" is +25%. "
"RR O2 SENSOR" should be below O.43V at least once when the "FUEL INJECTION" is -25%.

OR

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




(2) Set voltmeter probes between ECM terminals (52)-(sensor signal) and (43)-(engine ground).
(3) 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 O.48V and below O.43V at least once during this procedure. It the voltage can be confirmed in step 3, step 4 is not necessary.

4) Keep vehicle 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 O.48V and below O.43V at least once during this procedure.

CIRCUIT DIAGRAM





DIAGNOSTIC PROCEDURE





COMPONENT INSPECTION







Rear heated oxygen sensor heater
Check the following.
1. Check resistance between terminals (1) and (4).

Resistance: 2.3 - 4.3 Ohms [at 25°C (77°F)]1

2. Check continuity.
If NG, replace the rear heated oxygen sensor.

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.