GMC 2002 Yukon XL Owner's Manual page 281

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The seven 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
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Light Green: Back up Lamps
D
Red: Battery Feed
D
Dark Blue: Trailer Brake
If you need to upgrade your vehicle to heavy
trailering, a brake controller harness is available from
your dealer.
4-70
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Heavy Duty Trailer Wiring Package (If Equipped)
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duty
Your vehicle is equipped with the seven
towing harness. This harness with a seven
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heavy duty trailer connector that is attached to a bracket
on the hitch platform.
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wire trailer
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pin universal