Diagnostic Aids

WARNING: This page is about a different variant/trim than selected.

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness.

With ignition on and engine off, HO2S voltage on scan tool should gradually decrease to less than .15 volt indicating heater is operating properly. If voltage does not decrease as specified, disconnect HO2S connector and connect a test light between HO2S connector terminals "C" and "D" (engine harness side). If test light illuminates, replace HO2S. If test light does not illuminate, repair open in HO2S heater ground circuit or HO2S ignition feed circuit.

Using scan tool, monitor signal voltage while wiggling HO2S related connectors and wiring harness with a warm engine running at part throttle in closed loop. If a failure is induced, signal voltage will change from normal fluctuating voltage of greater than .6 volt and less than .3 volt, to a fixed voltage of about .45 volt. A change in voltage will assist in isolating location of fault. DO NOT solder HO2S wires.