2008 Chevrolet Silverado 1500 Pickup Owner's Manual - Page 403

Heavy-Duty Trailer Wiring Harness Package *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 your vehicle has an auxiliary battery. If your vehicle does not have an auxiliary battery, have your dealer or authorized service center install the required fuse. If you are charging a remote (non-vehicle) battery, press the tow/haul mode button 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, you can turn on the headlamps as a second way to boost the vehicle system and charge the battery. For vehicles equipped with heavy duty trailering, the harness is connected to a bracket on the hitch platform. 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* 4-91