I know I am a bit late but have had this problem in my 16 ltz and just final solved that problem in june of this year. All the stuff mentioned just wasted my time over the last couple years casing that message on the dash!! Though it was my new trailer for the longest time but it also did it with my dump trailer to. Problem seemed to be the worse on rainy days but wasn't limted to wet days. Turned out to be my factory 7/4 way combo and some module. The final straw for me was an 1-1/2 of it dinning back an fourth down the highway from my in-laws place to home! What the OP has stated only got worse with my truck. Fortunately I have a great relationship with my local dealership and they know I pull my work trailer almost daily. Not saying you don't possibly have something simple going on, just my experience with one of the newer platform problems. Never really had any problems with my 2011 2500 hd. Good luck Sent from my SM-G930V using Tapatalk