Service Stailitrak, Trailer Brake System, ABS lights

[Charlie Brown]

2017 GMC Sierra.  I plugged in a trailer and these lights have come on and will not clear.  I have had this truck in to check it out and the code said to replace rear driver sensor.  Which I did, but it did not fix the problem.. NO one can figure this out,a nd GM is telling me that a mouse or squirrel must have eaten a wire.  Which i find Unlikely.

I seen other members have had this issue but I can't find the Fix.  Anyone help me out?