GMC 2002 Envoy - Manual (Page 284)

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Trailer Wiring Harness Your vehicle is 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:
D Yellow: Left Stop/Turn Signal
D Dark Green: Right Stop/Turn Signal
D Brown: Running Lamps
D White: Ground
D Light Green: Back
- up Lamps
D Red: Battery Feed
D Dark Blue: Electric Brakes
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 is also 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.