Where do you plug in the trailer brake controler harness

question edited for clarity typos and spelling, break/brake, 'peddle/pedal.
Question move to model category.

Incorrect wiring or bad earths on the trailer (common issue)

https://www.google.com/search?q=2001+gmc+2500+hd+trailer+wiring+diagram

There is none from the factory. You have to splice the wires from the controller into the vehicle harness and run a wire to the trailer brake pin in the socket where the trailer cord plugs into the truck

hi, dear friend, I think this tool is your looking for.

You are probably going to find four wires together that do not have a plug on them. There should also be a tag taped on the wires showing that it is for the trailer. You will have to put a plug or some kind of connection on those wires.

The controller should have wiring diagrams with it. Also try http://www.etrailer.com/faq-wiring.aspx. The truck should have a harness that plugs into the factory harness under the dash. The harness paperwork will describe where it plugs into and what wires go where along with fuse location. If you don't hav the harness, you can get it from the dealer or the site listed above.

power wire should connect through a 30 amp resetting circuit breaker directly to the hot terminal of the battery. Brake line should be the same.

easiest way is to also buy the wiring adapter almost all elect brake units sell a vehicle specific wire harness that u unplug brake wire harness plug in other harness than plug in brake harness and just connect the wires to elect brake controller eliminates cutting and splicing ur brake harness about $18

Do you have brake lights on truck? Is this a new hook-up or has it been hooked up before & worked fine? If your brake lights on truck are one color (red) and your turn signals are another (amber) you will need to buy & connect a small converter that goes in harness to plug in order to separate the 2. Instructions with converter are pretty simple.

I found the problem. Talking with a technician from the controller company, we determined that it was a fuse problem. I found that the fuse to the CHMSL was blown.

The connector is located under the dash on the left side of the steering column. Their is a box, remove the cover and starting from the top left the second connector location moving to the right is the one to hook into, make sure that you have the correct wiring harnass adapter for the vehicle, their are two different ones for GM trucks. On the inside of the cover is also a diagram of the lay out of the box.