See also:

Telephone
...

Issuing a warning
If the vehicle begins leaving the lane and a lane marking has been detected, the steering wheel begins vibrating. If the turn signal is set before the lane is changed, a warning is not issued. ...

Switching on/off manually
Press the button. On: the LED lights up. Off: the LED goes out. If Top View is displayed, switch on the backup camera via the iDrive. ...