See also:

Deactivating HDC
Press the button again; the LED goes out. HDC is automatically deactivated above approx. 37 mph/60 km/h. ...

Enabling operation in the rear
Only possible via the iDrive in the front. 1. "Settings" 2. "Allow rear control" 3. Select the desired priority. ...

Malfunction
A message is displayed in the instrument cluster. HDC is not available, e.g., due to elevated brake temperatures. ...