2003 GMC Sierra 1500 SLE and "upfitting" (electrical)

[GeeNellyGMC]

I've got a 2003 Sierra SLE Extended cab. Can anyone tell me about upfitting connections in the under hood fusebox and others. Would my truck have a "7 pin harness" somewhere tucked up near the spare, or would that have been an option.

I found the 4 pin harness. Under the hood and in the rear would there be power and brake actuator wires related to the trailer?

I also wonder if installed the factory fog light switch would the bcm have to be programmed to enable this under the hood?

Thanks

 

[asilverblazer]

Sounds like you are referring to trailer wiring - If memory serves, a 7 pin harness is taped above the spare tire for trailering (if it isn't already terminated in the plug on the bumper).

 

A separate 4 pin harness that plugs into the BCM and is connected to an aftermarket brake controller is done under the dash. Lastly, a wire (red with black tracer taped along the main harness next to the fuse box) must be connected to the extra terminal on the side and corresponding fuse installed (30 amp maxi).