GMC 2010 T-Series, Owner'S Manual

Page: 147 / 294

Trailer Connections
(T7/T8 Models Only)
If the vehicle has these trailer connections, they are
located at the rear of the cab for a tractor and at the
rear of the chassis when towing a trailer. There will be
an air connection and an electrical connection.
Be sure that the couplings to the trailer are made
correctly.
Air Connections
If the trailer air line connections will not be connected to
another piece of equipment, be sure to replace their
protective caps.
Electrical Connections
This system is a seven-wire cable that will connect to
the trailer, supplying power to the trailer's lighting
system. When not in use, it is stored in the trailer
air-hose storage bracket.
Heavy-Duty Trailer Wiring Package
The vehicle may have an eight-wire trailer towing
harness. This harness, with a seven-pin universal
heavy-duty trailer connector, is attached to a bracket on
the platform hitch.
The Center High-Mounted Stoplamp (CHMSL) wire is
tied next to the trailer wiring harness for use with a
trailer.
The eight-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
. Light Blue: CHMSL
. Red: Battery Feed
. Dark Blue: Trailer Brake
4-25