Been fighting with the trailer wiring on this since I realized backup lights didn't go through to the plug. The back on the existing socket is all potted so I can't pull it apart and fix it. I think they cut the back off a normal one to make it fit where it was so I need to poke a hole and relocate it. I cut a hole in the bed and ran a wire up for a gooseneck plug and got that all tied into the truck wiring after finding the GREAT resource of the ram body builder's guide. Gives full info on all the good stuff cab & chassis trucks come with.
Before I did the second half of the work at lunch yesterday and installed the rear socket I double checked the pinout and all was good except for the thing that forced my hand on redoing the wiring in the first place: the +12v from the battery hadn't been wired in at all before, but the RD/VT wire that's supposed to carry is is dead. Key off or key on. So I need to track that down now, or run a new wire from the front of the truck. Shitty.
I haven't tested with the P3 standalone on the trailer with the hydro actuator but I have this sinking feeling that it's not going to do any better after getting this all fixed as far as thinknig it doesn't have a trailer connected even though it's set to hydro, and is supposed to all play nice together.