Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
The backup alarm could be wired to the reverse switch or to one of the reverse light bulbs. Since it comes on when you turn the headlights on I would assume that it is wired to the reverse light bulb and there is a short causing the tail light to power the backup alarm. When you turn the lights on do the reverse lights turn on also?