GMC 2006 Sierra - Manual (Page 405)

If your trailer is equipped with electric brakes, you can
get a jumper harness (electric trailer brake control)
with a trailer battery feed fuse from your dealer.
If you need to tow a light-duty trailer with a standard
four-way round pin connector, you can also get an
adapter form your dealer.
Heavy-DutyTrailer Wiring Harness
Package
For vehicles equipped with heavy duty trailering, the
harness is connected to the trailer plug mounted to the
hitch platform.
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
* The Center High-Mounted Stoplamp (CHMSL) wire
is tied next to the trailer wiring harness for use with
a trailer, slide-in camper or cap.
**If you are charging a remote (non-vehicle) battery,
turn on the headlamps to boost the vehicle system
voltage and properly charge the battery.
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