Diagnostic Aids

Normal scan tool reading in closed-loop will show O2S voltage varying between 150-850 millivolts.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.