DTC Confirmation Test (Overall Function Check)

WARNING: This page is about a different car, the 2002 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the following test to check overall function of 3-way catalyst. During this test, DTC may not be confirmed.

Malfunction is detected when 3-way catalyst does not operate properly. Possible causes are:

Defective 3-way catalyst.
Exhaust system damaged or leaking.
Intake air leak.
Defective injectors.
Defective spark plug.
Ignition timing incorrect.

CAUTION: DO NOT use ECM ground terminals when measuring voltage.

To check overall function of 3-way catalyst, start engine and drive vehicle at 44 MPH or more for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between ground and front HO2S signal circuit at ECM terminal No. 50 (Light Green wire) by backprobing. Using a second voltmeter, measure voltage between ground and rear HO2S signal circuit at ECM terminal No. 56 (Brown wire) by backprobing. See Figure and Figure . Increase engine speed to 2000 RPM. Switching frequency of rear HO2S should be less than 75 percent of front HO2S switching frequency. If front HO2S does not switch more than 5 times within 10 seconds, diagnose front HO2S first. See DTC P0133: FRONT HEATED OXYGEN SENSOR . If operation is not as specified, perform DIAGNOSTIC PROCEDURE .