With ignition "OFF", reconnect the HO2S connector

Warm up the engine to normal operating temperature and let it idle.

Connect Scantool and monitor the O2 SNSR VOL.-B1/S2 parameter on the Scantool data list.

Is sensor data near the specified value?

YES

▶ Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure

NO

▶ Check HO2S for contamination, deterioration, or damage. Substitute with a known-good HO2S and check for proper operation. If the problem is corrected, replace HO2S and then go to "Verification of Vehicle Repair" procedure