DTC Confirmation Test (Overall Function Check)

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

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

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

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

To check overall function of three-way catalyst, start engine and drive vehicle at 43 MPH or more for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between ground and ECM terminals No. 82 (right front HO2S signal) or No.83 (left front HO2S signal), and No. 89 (right rear HO2S signal) or No. 90 (left 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: LEFT SIDE FRONT HEATED OXYGEN SENSOR (HO2S), OR DTC P0153: RIGHT SIDE FRONT HEATED OXYGEN SENSOR (HO2S) .