Am curious, does your brake pedal switch look like the below images?
This is the key to having an after market trailer brake controller
lead the trailer brakes before the TV's brakes ever get turned on

GMBrakeSwitch brakeswitch
These pics for my reference for next discussion on trailer brake controller
and how the GM is different with less than 0.010" travel to turn on
the brake lights




Jframpey wrote:
Hmmm, i recently replaced the brake light switch (on the brake pedal) after getting a cruise control error - After an internet search told me that this was the probable culprit. I have a 08 2500 chevy - I had no issues with the IBC that I know of, but I don't recall towing while I had the issue either.
Changing the brake switch $35 fixed my problems... I took the old brake switch apart after the repair and found it gummed up with grease (someone was overzealous with it during assembly I guess. Anyway I found that the switch had two sets of contacts - one normally open and one normally closed. Check yours out - maybe its the culprit.