Diagnostic Aids

Check for poor connection at PCM. Check for damaged wiring harness. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation.

Turn ignition on, with engine off. Using scan tool, monitor HO2S 1 voltage. Voltage should gradually drop to less than 250 mV or rise to greater than 600 mV. If voltage is not as specified, disconnect HO2S 1 connector. Connector a test light between ignition feed circuit and heater ground circuit terminals at HO2S 1 harness connector. If test light does not illuminate, repair open ignition feed circuit. If test light illuminates, replace HO2S 1.