What do I need to add the electric brake controller to my 2009 xl screw.
It has the 4 pin connector.

 

The harness was below the 4x4 switch on mine, it was plugged into the back of change tray. You'll see it when pull out the tray to install the controller. The dealer will have to flash the computer to make it work.

I also had to put in a relay and fuse under the hood in the fuse box above the radiator. Those came with my truck when I bought it.

I'm not sure about just having a flat 4 connector, because I had both 4pin and 7pin..

Hope that helps.

 

Trailer brakes will not work with a 4-pin connector.

 

You will have to buy the 7-pin rear harness. You will have to unplug the 4-pin harness and plug the new harness in. It's located under the rear bumper along the frame.