Can Brake Controller Cause the Trailer Running Lights Not to Work and Fuse Blow on 2007 GMC Sierra

Published 10/10/2012

Question:

I bought my hitch from you guys awhile back on my then 2001 Toyota tundra. I recently bought a 2007 GMC Sierra 2500HD Classic 4x4 long bed 6.6 Diesel. I swapped over the Prodigy P2 Brake Controller from my tundra over to the Sierra and everything seems to work fine brakes, brake lights, turn lights, hazards, Except the trailer running/parking lights. I found that the fuse under the hood for trailer park was blown. When I replaced the fuse, it blew again. So I am thinking that when I spliced the P2 controller to the old adapter that was in the truck previously that I must have maybe? spliced the wrong colors? Although I matched the colors to themselves. Black=black, blue=blue, etc... I dont know just a thought? I did some research on various forums and heard that chevy/gmc made different adapters for different years so sometimes the blue and brownrunning lights are switched on the plug-in wiring harness? So do you guys offer different plug in wiring harnesses for different year 2500hds? Do you think that a new plug-in wiring harness could do the trick?

asked by: Dave H

Expert Reply:

It might not be the brake controller that is causing the problem. It sounds like there could be a short on the trailer that is causing the fuse to blow. You will want to check the trailer wiring and make sure there are no nicks in the wiring that might have exposed wire touching the metal of the trailer frame. Also check the truck and trailer side connectors for corrosion that might be causing a short. Corrosion can also build up behind the connectors where the wires attach.

The 7-Way wiring harness that we have for the 2007 GMC Sierra Classic is # 30955. This is used either as a replacement if the factory 7-Way got damaged or to add one to a truck that did not come with a 7-Way.

For the brake controller you should be using wiring harness # 3015-P. I have included instruction and video links showing a typical installation. On the wiring harness the white wire is ground, the black wire is 12 volt power, the blue wire is output to the trailer brakes, and the red wire is input from the brake switch.

There are different brake controller wiring harnesses for different years as well as different makes and models. Your truck uses # 3015-P.

expert reply by: Michael H