GMC 2013 Sierra Denali Owner's Manual page 303

The seven-wire harness contains
the following trailer circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn
Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Red: Battery Feed*
Dark Blue: Trailer Brake*
*The fuses for these two circuits are
installed in the underhood electrical
center, but the wires are not
connected. They should be
connected by your dealer or a
qualified service center. The fuse
and wire for the ITBC is factory
installed and connected if the
vehicle is equipped with an ITBC.
The fuse for the battery feed is not
required if the vehicle has an
auxiliary battery. If the vehicle does
not have an auxiliary battery, have
your dealer or authorized service
center install the required fuse.
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
located under the front edge of the
pickup box on the driver side of the
vehicle, attached to the frame
bracket. A connector must be added
to the wiring harness which
connects to the camper.
The harness contains the following
camper/trailer circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn
Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Red: Battery Feed
Dark Blue: Trailer Brake
If the vehicle is equipped with the
Heavy-Duty Trailering option,
please refer to Heavy-Duty Trailer
Wiring Package earlier in this
section.
When the camper-wiring harness is
ordered without the heavy-duty
trailering package, a seven-wire