WARNING: This page is about a different car, the 2011 BMW M3, 2010 BMW M3, 2009 BMW M3, and 2008 BMW M3. 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 Using Special Tool (61 1 360)