DTC Confirmation Test (Overall Function Check)

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.

Start engine and drive vehicle at 43 MPH or more for 2 minutes. Stop vehicle and leave engine running. Using 2 DVOMs, backprobe ECM harness connector. See Figure. Connect one DVOM between ground and terminal No. 62 (White wire) at ECM harness connector, then connector the other DVOM between ground and terminal No. 63 (Blue wire) at ECM harness connector. See Figure. Increase engine speed to 2000 RPM. Switching frequency of front HO2S divided by switching frequency of rear HO2S should be less than .75. If front HO2S does not switch more than 5 times within 10 seconds, diagnose front HO2S first. See DTC P0133: FRONT HEATED OXYGEN SENSOR .