Diagnostic Aids

An intermittent problem may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for poor connection or damaged harness. Inspect PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. Faulty Engine Coolant Temperature (ECT) sensor. Using scan tool, compare engine coolant temperature with intake air temperature on a completely cool engine. Engine coolant temperature should be within 50 °F (10 °C) of intake air temperature. If not, replace the ECT sensor.