The 1999 GMC Jimmy light-duty trailer wiring is a six-wire harness assembly. The harnesses are stored under the vehicle, along the passenger-side frame crossmember on two-door vehicles or on the driver’s side corner frame rear crossmember on four-door vehicles. The heavy-duty trailer wiring has a 30-amp feed wire with an inline fuse located by the junction block. 1999 GMC Jimmy Trailer Wiring Harness Color Code are as follows:
Dark Blue: Use for electric trailer brakes or auxiliary wiring.
Brown: Taillamps and parking lamps.
Yellow: Left stoplamp and turn signal.
Dark Green: Right stoplamp and turn signal.
White (Heavy Gauge): Ground wire.
White (Light Gauge): Auxiliary stoplamp.