61 13 ... Circular Plugs, 20-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.
Carefully press back retaining lugs (1) of internal connector (2).
Turn internal connector (2) enough for retaining lugs (1) to lock into locking groove (3).
With special tool 61 1 132 (ejector), press back arrester hook (4) of appropriate contact and pull out cable.