Originally Posted by mike.t
Reset the computer?? Do you mean reprogram the towing mode?
Disconnect the battery for 30 seconds and reconnect it.
Originally Posted by RollingDownTheHighway
I would try towing a different trailer with elect brakes or have someone tow your TT. It may not be your truck, it may be with your TT electrical system messing up your truck or maybe rent a truck and tow your TT and see if that truck does the same thing. If it only happens when you're towing our TT, it may not be the truck.
The trailer brake, anti lock, stability and sway control on these trucks is not a new system and has been in place in almost the same form since 2010. Its not known to have a lot of issues.
It is very sensitive to two things. First it does not like it when you plug in or unplug the 7 way while the truck is running or the ignition is on. A lot of times doing that will throw the computer into doing exactly what the OP describes. My 2015 GMC 2500 has done it once, and my 2013 Chevy before that also had done it. Disconnecting the battery and reconnecting took care of it.
It also does not like any voltage fed into the trailer brake system from another source, such as the break away switch. I had a moron pull my break away while still plugged in when doing my trailers state safety inspection. That was despite me specifically telling him beforehand to disconnect the 7 way before he checked it. That fired off the ABS, Check Engine, and Stabiltrak control lights as well as lighting up the DIC with "check trailer wiring" and "service trailer brakes" messages. A hard reboot by disconnecting the battery reset everything.