Quick question. Do the plug ends correspond to the same wires as in D to D, C to C, etc.? Mine do not on the harness. My problem is that when the lights come on the brakes will drag anywhere from .8 to 2.0. It will also occur if I disconnect the trailer and then turn the lights on.

I am not sure if I really understand your symptoms but there are two different versions of the harness. After 2002 or 2003 Chevy switched some of the wires so you might have the harness for the earlier trucks and you need the one for the later trucks.

After I did some searching it turns out they sent me a pre-03 harness. I swapped the red stoplight wire to the other slot and all is well. Thanks for your help.