Global Machinery Company Sierra 1999 - Manual (Page 256)

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Basic Trailer Wiring Package (Diesel Engine)
Regular and extended cab pickups equipped with a
6.5L Turbo Diesel engine have an eight
- wire trailer
towing harness.
The trailer wiring harness with a seven - pin connector
and separate Center High - Mounted Stoplamp (CHMSL)
connector are located at the rear of the vehicle and are
tied to the vehicle’s frame.* The harness connector can
be plugged into a seven
- pin universal heavy-duty trailer
connector available through your GM dealer.
* The single CHMSL wire is tied to the seven - wire
harness and is used if your trailer or cap are equipped
with a CHMSL.
The eight - wire harness contains the following
trailer circuits:
D Yellow: Left Stop/Turn Signal
D Dark Green: Right Stop/Turn Signal
D Brown: Taillamps
D White: Ground
D Light Green: Back
- up Lamps
D Light Blue: CHMSL
D Red: Battery Feed
D Dark Blue: Trailer Brake
If you need to upgrade your vehicle to heavy
- duty
trailering, a brake controller harness and a seven - pin
universal heavy - duty trailer connector are available
from your GM dealer.