Diagnostic Aids
Intermittent condition can be caused by a poor connection, rubbed-through insulation or a wire that is broken inside the insulation. The frequency of the malfunction can be checked by using the enhanced diagnostic function of the Tech 1 scan tool as described in the manual supplied with tester.
Any circuit that is suspected of causing an intermittent complaint should be thoroughly inspected for backed-out terminals, improper mating, broken connector locks, improperly formed or damaged terminals, poor terminal-to-wire connections or physical damage to the wiring harness.
Also, verify proper stoplight switch operation using scan tool display. As the brake is applied the tester should display "on" status within one inch of travel.