2005 GMC Envoy Owner's Manual - Page 331

Trailer Wiring Harness Brown: Running Lamps White: Ground Light Green: Back-up Lamps Dark Blue: Electric Brakes Red: Battery Feed (The chassis wiring ring terminal must be fastened to a stud on the underhood electrical center before the trailer feed will become active.) If you need to tow a light-duty trailer with a standard four-way round pin connector, an adapter connector is available from your dealer. Your vehicle may also be equipped with wiring for an electric trailer brake controller. These wires are located inside the vehicle on the driver's side under the instrument panel. These wires should be connected to an electric trailer brake controller by your dealer or a qualified service center. Your vehicle may be equipped with the seven-wire trailer towing harness. This harness has a seven-pin universal heavy-duty trailer connector that is attached to a bracket on the hitch platform. The seven-wire harness contains the following trailer circuits: • Yellow: Left Stop/Turn Signal • Dark Green: Right Stop/Turn Signal 4-65