61 13 ... Circular Plugs, 13-Pin, System D2.5
WARNING: This page is about a different car, the 2007 BMW 550i and 2006 BMW 550i. However, it is still accessible from the selected car via links, so may be relevant.
Pull off rubber grommet (1).
Carefully pull out lock (2) in direction of arrow.
Move connector lower section (3) in direction of arrow enough for retaining lugs (4) to lock into locking groove (5).
Using special tool 61 1 132 (ejector), press down retaining hooks (6) on appropriate contact and pull out cable.