Pinpoint Test C5 - Check Wires To Headlight Control Module
With headlights on, measure and note voltage on Red/Black wire at headlight control module. With high beams on, measure and note voltage on Red/White wire at headlight control module. If voltage is greater than 10 volts in either case, go to test C6. If voltage is less than 10 volts in either case, service wire(s) in question.