2005 gmc sierra crew cab - brake controller issue
 

I dont know what to do anymore. I've tried 2 new electronic brake controllers, i bypassed the blue wire and bouvht a new truck side trailer plug end. Everything works great on my new travel trailer, but when i apply the brakes i get a " over load l" code on my brake controller. They work for a second then throws the error code. Or they work at slow speeds, sometimes giving the error , sometimes not. The internet says its a short on the blue 7 pin wire, but ive already tried and bypassed it from the back of the controller, to the back of the truck side of the 7 pin connector. Any ideas??