Trailer wiring - OEM harness issue - no power for lights or brakes?? brak

[myeaglescout]

I recently picked up a BMW oem trailer hitch and 7 terminal wiring harness (labeled POLLAK on the flip up door) from the upullit yard here. I have a 2001 X5 and it was in a 2002 X5. When installing into my 2001, I found the same original plug in my trunk area (it had an empty plastic plug end in it to keep it from being accidentally grounded and to keep it clean), but the only power I can read in that plug is the always hot terminal, and the ground. None of the other lights have any output there. Is there something I'm not doing right? I have not been able to find an installation guide anywhere online, so I was hoping someone out there might know if I need to add fuses somewhere, or flip a switch or hook up another harness connector. I did notice a white connector up in front of the spare on the right that looks to have the same type of connector as the black one in the rear, but it's too far away to be the one for the trailer harness.