DTC Confirmation Test (Overall Function Check)

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

Malfunction is detected when switching frequency of rear HO2S increases to a specified value, indicating that three-way catalyst does not operate properly. Possible causes are:

Defective three-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 three-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 ground and ECM terminals No. 63 (right front HO2S), No. 62 (left front HO2S), No. 72 (right rear HO2S) and No. 71 (left rear HO2S) 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 operation is not as specified, go to PROCEDURE . If front HO2S does not switch more than 5 times within 10 seconds, diagnose and repair front HO2S. See DTC P0133: RIGHT BANK, OR DTC P0153: FRONT HEATED OXYGEN SENSOR .