Diagnostic Aids
Using scan tool, monitor electrical load parameter. When rear defogger and/or headlights are turned on, scan tool should indicate on. When rear defogger and/or headlights are turned off, scan tool should indicate off.
An intermittent condition may be caused by a poor connection, rubbed-through wire insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, or damaged harness.