E53 trailer hitch install - What does the 15-pin trailer module X609 do??
 

What does the 15-pin trailer module X609 actually do when I plug it in? Is it telling the X5's computer that I now have a trailer hitch installed and thus changes the transmission gear changing? I hope not!! I am not towing stuff very often and would hate for it to change how my X5 drives! Maybe it only interacts if a brake controller is installed (which I do not have)?

Does anyone know what exactly this X609 module does? Thanks!

no, it controls the lights on the trailer to match that of the car, sends over the brake signals if you have a brake controller, turns off rear pdc when the plug is in, does send some power to the trailer for charging/etc of the trailer's elec system.. and a few other things i'm sure...