[Ski-me]

This is a helpful wiring diagram and notes on color coordinating....

http://www.etrailer.com/faq-wiring.aspx

Look in your engine compartment just next to the brake booster (or underneath and right). There may be some thicker wire bundle (blue and red) that is set up from factory to use for trailer brakes. You can use these to hook up a controller inside and the use the same in the back. Depending on the style, you may have something old (4 or 5 pin round). Hard to say but the best method is to break out a tester.

I originally had a round, 5 plug setup on my K-5 and converted it over to the more common 7-spade circle connector. I used my 04' suburban with a factory connector as a confirmation check.