WARNING: This page is about a different car, the 2013 BMW X5 M, 2012 BMW X5 M, 2011 BMW X5 M, and 2010 BMW X5 M. However, it is still accessible from the selected car via links, so may be relevant.
Unlock hooks (1) with special tool 61 1 360 and push plug housing out of the socket.
Fig 1: Unlocking Hooks With Special Tool (61 1 360)