Here's an unusual situation - I just bought a 2004 K2500HD crew cab Duramax with the ZF 6 sp manual. It has the factory trailer hitch and wiring. The wiring diagram I have says that there are wires stowed under the instrument panel to connect the trailer brake controller. After some more investigation and research I found that there is supposed to be a short wire harness for the brake controller plugged into the relay box near the top of the clutch pedal. I found the relay box and identified the empty connector for the controller haness. It looks like a former owner may have removed the harness when they removed a brake controller in the past. I checked with the local Chevy dealer to see if this harness is a part I can buy and all I got was - "never heard of it".
Anyone got any ideas as to whether I can get tis part from Chevy.
I can splice into the harness under the dash as a last resort.

 

http://www.draw-tite.com/prodphoto/gif/18267.gif there are the pig tail harness available from many different suppliers that sell brake controls .do not try to hard wire it .this is a sample ,drawtite ,valley ,hidden hitch,reese.