66 20 535 Removing and installing/replacing a rear right ultrasonic transducer (Park Distance Control)
WARNING: This page is about a different car, the 2013 BMW Z4, 2012 BMW Z4, 2011 BMW Z4, 2010 BMW Z4, and 2009 BMW Z4. However, it is still accessible from the selected car via links, so may be relevant.
The following operation is described in:
Removing REAR LEFT ULTRASONIC TRANSDUCER