With CONSULT
ON-BOARD DIAGNOSIS LOGICThe 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 DTC DETECTING CONDITION, the following method can be used for checking the rear heated oxygen sensor function. (The "NG" of the OVERALL FUNCTION CHECK means the same as the DTC detection.)
1. Start engine and warm it up sufficiently.
2. Select "FUEL INJECTION" in "ACTIVE TEST" mode, and select "RR O2 MNTR" as the monitor item with CONSULT.
3. Check "RR O2 MNTR" at idle speed when adjusting "FUEL INJECTION" to ±25%.
"RR 02 MNTR" should be "rich" when the "FUEL INJECTION" is +25%.
"RR 02 MNTR" should be "lean" when the "FUEL INJECTION" is -25%.
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 52) 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.