WARNING: This page is about a different car, the 2003 BMW 530i, 2002 BMW 530i, and 2001 BMW 530i. However, it is still accessible from the selected car via links, so may be relevant.
Switch off ignition.
Remove ignition coils.
Detach ignition coil (1) from spark plug connector (2).
Fig 1: Detaching Ignition Coil From Spark Plug Connector