See also:

Guide lines in the COMAND display
WARNING   Use of rear view camera can be dangerous if you are color-blind or have impaired color vision. Only use rear view camera if you can see and distinguish all colored guidelines ...

The windshield wipers are obstructed
Leaves or snow, for example, may be obstructing the windshield wiper movement. The wiper motor has been deactivated. For safety reasons, you should remove the SmartKey from the ignition lock. ...

Monitoring range of the sensors
Blind Spot Assist monitors the area shown in the figure up to 10 ft (3 m) behind and immediately adjacent to your vehicle. WARNING   Blind Spot Assist monitors certain areas in the im ...