Auxiliary Battery; Trailer Recommendations - GMC Sierra 2008 Owner's Manual

When the camper-wiring harness is ordered without the
heavy-duty trailering package, an eight-wire harness
with a seven-pin connector is located at the rear of
the vehicle and is tied to the vehicle's frame.
Electric Brake Control Wiring
Provisions
These wiring provisions are included with your vehicle
as part of the trailer wiring package. These provisions
are for an electric brake controller. The instrument panel
contains blunt cut wires near the data link connector
for the trailer brake controller. The harness contains
the following wires:
•
Dark Blue: Brake Signal to Trailer Connector
•
Red/Black: Battery
•
Light Blue/White: Brake Switch
•
White: Ground
It should be installed by your dealer or a qualified
service center.
If your vehicle is equipped with an ITBC, the blunt cuts
exist, but are not connected further in the harness.
If you install an aftermarket trailer brake controller,
the ITBC must be disconnected. Do not power both
ITBC and aftermarket controllers to control the trailer
brakes at the same time.
4-90

Auxiliary Battery

The auxiliary battery provision can be used to supply
electrical power to additional equipment that you
may choose to add, such as a slide-in camper. If your
vehicle has this provision, this relay will be located
on the driver's side of the vehicle, next to the underhood
electrical center.
Be sure to follow the proper installation instructions that
are included with any electrical equipment that you install.
Notice: Leaving electrical equipment on for
extended periods will drain the battery. Always turn
off electrical equipment when not in use and do
not use equipment that exceeds the maximum
amperage rating for the auxiliary battery provision.

Trailer Recommendations

You must subtract your hitch loads from the CWR for
your vehicle. Weigh your vehicle with the trailer
attached, so that you won't go over the GVWR or
GAWR. If you are using a weight-distributing hitch,
weigh the vehicle without the spring bars in place.
You'll get the best performance if you spread out the
weight of your load the right way, and if you choose the
correct hitch and trailer brakes.
For more information, see Towing a Trailer on page 4-54.