66 20 537 Removing and installing/replacing a rear middle right ultrasonic transducer (Park Distance Control)
WARNING: This page is about a different car, the 2013 BMW X5, 2012 BMW X5, and 2011 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Operation is described in:
Removing and installing/replacing REAR MIDDLE LEFT ultrasonic transducer