Trailer light Issues

[HTOWN///M]

Hey guys, im having an issue with my 2004 e53 4.4. Ive own the X5 for just over 2 months. It came with a pre-installed trailer hitch and trailer light socket. Never questioned it since it all looked factory etc. Well i just bought a new car hauler today and I picked it up with an ford excursion. lights all worked, turn signal etc. I get home and hook it up to the X5 and nothing. No lights nothing. So i figure maybe blown fuse or something. Check everything and its all good. So next option was to check to make sure I had power at the trailer socket on the X5. I have power but its fluctuates a lot. from 0 back up and so forth. I checked the trailer socket on the ford excursion and the voltage stay constant. so i assume that is my issue. Both the ford and the X5 are 4 pin and the trailer is a 7 pin but obviously that doesn't matter on the ford.

I did check the power coming into the control box that is by the battery and i'm getting constant power to it but after that box it appears the power fluctuates. So i'm at a lose. I cant figure it out . is there something i'm missing?

The e53 isnt new enough to need coding,is it?

Any insight will help