Heavy-DutyTrailer Wiring Harness Package

GMC Sierra / GMC Sierra Owners Manuals / Driving and Operating / Towing / Towing Equipment / Heavy-DutyTrailer Wiring Harness Package

For vehicles equipped with heavy duty trailering, the harness connector is mounted in the bumper.

For vehicles equipped with heavy duty trailering, the harness connector is mounted in the bumper.

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.

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