See also:

Range of the sensors
General notes The sensors must be free of dirt, ice and slush; otherwise they may not function correctly. Clean the sensors regularly, taking care not to scratch or damage them. Side view ...

Important safety notes
WARNING   The PARKTRONIC is a supplemental system. It is not intended to, nor does it replace, the need for extreme care. The responsibility during parking and other critical maneuvers ...

BAS PLUS (Brake Assist System Plus)
BAS PLUS is only available in vehicles equipped with DISTRONIC PLUS. Observe the "Important safety notes" section. At speeds above approximately 20 mph (30 km/h), BAS PLUS assists ...