Without CONSULT

ON-BOARD DIAGNOSIS LOGIC
The rear heated oxygen sensor has a much longer switching time between rich and lean, due to the oxygen storage capacity of the up-stream three way catalyst. To judge the malfunctions of rear heated oxygen sensor, Engine Control Module (ECM) monitors the sensor's voltage value and the switching response during the various driving condition such as fuel-cut.




OVERALL FUNCTION CHECK
Instead of performing DIAGNOSTIC TROUBLE CODE (DTC) DETECTING CONDITION, the following method can be used for checking the rear heated oxygen sensor function. (The "NG" of the 0VERALL FUNCTION CHECK means the same as the DTC detection.)
1) Start engine and warm it up sufficiently.




2) Set voltmeter probes between ECM terminals 56 (sensor signal) and 25 (engine ground).
3) Check the voltage when racing up to 6,500 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 below 0.55 volts at least one time.

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 0.6 volts at least one time.




NOTE: After starting the engine, the output voltage of the rear heated oxygen sensor indicates higher voltage (approx. 5 volts at highest) than the normal operating range for about 7 seconds. This is due to checking for open circuits in rear heated oxygen sensor by on-board diagnosis. Therefore, if you measure the voltage (at ECM terminal 56) during this diagnosis, the higher voltage will appear.
(CONSULT will also show the higher voltage, Generic Scan Tool (GST) may show approx. 0 volts.) This is not a malfunction even though it is out of the normal range.