Diagnostic Aids

Check for exhaust system leaks, malfunctioning TWC, faulty oxygen sensors or fuel system problems. Repair all HO2S related DTCs first.

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.