I just purchased a used 2004 QC 4x4 CTD and am going to hook up my prodigy brake controller using the prewired connector to the blue plug under the dash. My question is this: at the rear of the truck is a flat four prong connector coming out of a black wire loom. I know that this is not sufficient to run trailer brakes and accessory wires, etc. I am wondering, did this truck have a 7 pin plug from the factory, and then the previous owner hacked it off to tow a small trailer, or do I just need to crawl under and find the blue wire that is for the trailer brakes. I already have the female 7-pin plug. I have not traced this wire the length of the truck, but I am curious where the blue trailer brake wire could be. Any advice before I start would be helpful. Thanks.

 

My last truck was an 04 and it had the 7 pin plug on the rear bumper AND the 4 pin plug. I also had the brake controller and plugged it in under the dash. It was too easy to just plug it in and screw it to the dash. I used the switch to hook and unhook the fifth wheel trailer. It's location may not be as necessary if you have a bumper pull trailer

 

Believe it or not, the trailer wiring (7 pin connector) is an option. I've personally never seen one come from the factory with out it, but it's possible...

I'd stop by Checker (Kragens?) or Autozone and see about a plug-and-play Hoppy or Pollak brand 7 pin wiring kit for your truck. They're about $25 the last time I checked (for a chebby I had), but well worth it. They usually just plug in line between the connector from the frame to the bed, no mods required. Not sure how they connect up with the trailer brakes.