I ordered my 2016 2500 Window with the optional AHT Mopar Trailer Tow Group. This gave me a 2" receiver hitch, along with a 4-way and 7-way connector. When I went to hook up my trailer to the 7-way, nothing worked. No parking lights, no turn signals/brake lights. I did have +12 volts on pin 5. After 3 trips to the dealer (70 miles round trip), they got things working by replacing the Trailer Brake Light Control Module. It is a 3" square box located in the left rear pillar about half-way up.
Come to find out that there is a recall for that very problem, but my PM is not on the list ??? The recall is FCA S22 or NHTSA 16V253000. Anyway, since I got the lights working, I asked the dealer if they had a connection diagram for the 7-way so that I could hook up a brake controller when I got one. No way. They said that their tech didn't even have a wiring diagram. Yeah, right.
Fast forward a couple of weeks. Today, I hooked up a Draw-Tite
#20191 controller.
https://www.amazon.com/Draw-Tite-20191-I-Stop-Electronic-Control/dp/B003CSNCUC
When I pulled the battery cover, there was a blue wire labeled Trailer Brake that goes to pin
#3 on the 7-way, and a red w/ blue wire coming off of the battery with a 20 amp fuse that goes to pin
#5 on the 7-way. I spliced the red w/blue wire past the fuse to get power for the controller (black wire on the controller). The blue wire from pin
#3 hooks to the blue wire on the controller. The white wire of the controller goes to ground, and the red wire of the controller goes to the brake switch pin
#4 ( the green w/white wire). See
http://www.rambodybuilder.com/2015/van/docs/vf/tbc.pdf
My trailer brakes are now functional. The only downside is that the Brake Controller has power to it all the time, even with the ignition off. I may install a relay later to have it work with the ignition "on" only.