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 switching frequency of rear HO2S increases to a specified value, indicating that 3-way catalyst is not operating properly. Possible causes are:

Defective 3-way catalyst.
Exhaust leak.
Intake air leaks.
Defective injectors.
Defective spark plugs.
Incorrect ignition timing.

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

To check overall function of 3-way catalyst, drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between engine ground and ECM terminals No. 62 (front HO2S) and No. 63 (rear HO2S) by backprobing. See Figure and Figure . Increase engine speed to 2000 RPM. Ensure switching frequency of rear HO2S is less than 75 percent of front HO2S switching frequency. If front HO2S does not switch more than 5 times within 10 seconds, diagnose and repair front HO2S. See DTC P0133: FRONT HEATED OXYGEN SENSOR (HO2S) .