Global Machinery Company Sierra 1999 - Manual (Page 257)

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Heavy - Duty Trailer Wiring Package (If Equipped)
Your pickup may be equipped with the eight - wire trailer
towing harness. This harness with a seven - pin universal
heavy - duty trailer connector is attached to a bracket on
the platform hitch.*
* 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.
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
A jumper harness for an electric trailer brake controller
and a trailer battery feed fuse are included with this
trailering package. (See “Instrument Panel Jumper
Wiring Harness” later in this section.)
If you need to tow a light - duty trailer with a standard
four - way round pin connector, an adapter connector is
available from your dealer.