DTC Confirmation Test (Overall Function Check)

NOTE: Use the following test to check overall function of 3-way catalyst. During this test, first trip 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 43 MPH or more for 2 minutes. Stop vehicle and leave engine running. Measure voltage between ground and ECM terminals No. 46 (front HO2S signal) and No. 52 (rear HO2S signal) 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 (HO2S) .