2004 GMC Sierra 1500 Pickup Owner's Manual - Page 394

Instrument Panel Jumper Wiring Harness {CAUTION: Be sure to use only the correct trailer brake harness, the one intended for use on your vehicle. If you use some other trailer brake harness, even if it seems to fit, your trailer brakes may not work at all. You could have a crash in which you or others could be injured. Use only the trailer brake harness intended for your vehicle. If it is no longer available to you, be sure to get a proper replacement from your dealer. If your vehicle is equipped with the "Heavy-Duty Trailering″ option, please refer to Heavy-Duty Trailer Wiring Package, earlier in this section. When the camper-wiring harness is ordered without the heavy-duty trailering package, an eight-wire harness with a seven-pin connector and separate CHMSL connector are located at the rear of the vehicle and are tied to the vehicle's frame. 4-98