General notes

If you cannot lock or unlock the vehicle with the SmartKey, either the battery in the SmartKey is discharged, the SmartKey is faulty or the starter battery is discharged.

SmartKey and replace it if necessary. Check the battery in the SmartKey and replace it if necessary.
mechanical key. Unlock the driver's door using the mechanical key.
mechanical key. Lock the vehicle using the mechanical key.
battery contacts checked at a qualified specialist workshop. Have the starter battery and the battery contacts checked at a qualified specialist workshop.

If the SmartKey is faulty, contact Roadside Assistance or a qualified specialist workshop.

    See also:

    Safety
    The 2012 M-Class was deemed a Top Safety Pick by the Insurance Institute for Highway Safety, meaning it received the top score of Good in front- and side-impact crash tests, as well as for roof st ...

    Exterior mirror out of position
    If an exterior mirror has been pushed out of position, proceed as follows: Vehicles without electrically folding exterior mirrors: move the exterior mirror into the correct position manually. ...

    Activating audio AUX mode
    When you connect an external audio source, audio AUX is not selected automatically. Select Audio in the main function bar by sliding and turning the COMAND controller and press to confirm. ...