that is a connector that runs from the back side of the front wall (as pictured) to the battery compartment, where another connector is present, to be plugged into the trailer module. The pictured connector connects to the harness that feeds through a hole in the body and routes outside, to the round connector for the trailer.

__________________
E53 X5 4.6iS
147K mi - Sold May 2013
Tireprints left in:
USA, Nicaragua, Costa Rica, Panama, Russia

E53 X5 4.8iS built 2005-10-17
66200 mi - June 2012
96000 mi - June 2013
112000 mi - June 2014
OEM fire extinguisher
OE first aid kit
OE tow hitch
OE TV module
OE aspheric mirror
K&N air filter
black/white badges
rear camera
4-channel video recorder

Here is the list of things I have done to the X