Basic Trailer Wiring; Heavy-Duty Trailer Wiring Harness Package; Camper/Fifth-Wheel Trailer Wiring Package - GMC 2014 Sierra Owner's Manual

All regular, extended cab, and crew
cab pickups have a seven-wire
trailer towing harness.
For vehicles not equipped with
heavy duty trailering, the harness is
secured to the vehicle's frame
behind the spare tire mount. The
harness requires the installation of a
trailer connector, which is available
through your dealer.
For vehicles equipped with heavy
duty trailering, the harness
connector is mounted in the bumper.
The seven-wire harness contains
the following trailer circuits:
Green/Violet: Left Stop/Turn
Signal
Yellow/Grey: Right Stop/Turn
Signal
Grey/Brown: Taillamps/
Parklamps
White: Ground
White/Green: Back-up Lamps
Red/Green: Battery Feed
Dark Blue: Trailer Brake
If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode
button, if equipped, located at the
end of the shift lever. This will boost
the vehicle system voltage and
properly charge the battery. If the
trailer is too light for Tow/Haul
Mode, or the vehicle is not equipped
with Tow/Haul, turn on the
headlamps as a second way to
boost the vehicle system and
charge the battery.
The seven-wire camper harness is
under the rear bumper, attached to
the frame near the rear
crossmember. A connector must be
added to the wiring harness that
connects to the camper.
The harness contains the following
camper/trailer circuits:
Green/Violet: Left Stop/Turn
Signal
Yellow/Grey: Right Stop/Turn
Signal
Grey/Brown: Taillamps/
Parklamps
White: Ground
White/Green: Back-up Lamps
Red/Green: Battery Feed
Dark Blue: Trailer Brake