GMC 2004 Sierra - Manual (Page 392)

The six-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: Center High-Mounted Stoplamp
(CHMSL)
If you need to upgrade your trailer wiring harness, an
additional 2–wire harness and 7 pin universal trailer
connector are available from your dealer.
Heavy-DutyTrailer Wiring Harness
Package
Your pickup may be equipped with the eight-wire trailer
towing harness. This harness with a seven-pin
universal trailer connector is attached to a bracket on
the hitch platform.
* 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.
4-96