Reducing the energy consumption of the key
If you do not use the vehicle or a key for an extended period, you may deactivate the KEYLESS START function of the key.
To deactivate:
press the 
button on the key twice in quick succession. The battery indicator lamp on the key lights up twice quickly and once for longer.
To activate:
press any button on the key. When starting the vehicle with the key in the slot in the shift console, the key functions are activated automatically.
Overview of the Mercedes-Benz emergency call system
The Mercedes-Benz emergency call system can help to decisively reduce the time between an accident and the arrival of emergency services at the site of the accident. It helps locate an accident site in places that are difficult to access.
The emergency call can be triggered automatically More.
You also have the option of triggering the emergency call manually More. Only make emergency calls if you or others are in need of rescue. Do not make an emergency call in the event of a breakdown or a similar situation.
Message in the media display:
SOS NOT READY: the ignition is not on or there is a malfunction with the emergency call system.
This does not necessarily indicate a total failure of the emergency call system. Emergency calls can still be transmitted.
The display refers only to the vehicle and does not take account of the availability of mobile phone networks and the Mercedes-Benz emergency call centre.
The functionality of the emergency call system on the vehicle can be seen when the SOS NOT READY display goes out when the ignition is switched on.
During an active emergency call, 
appears in the display.
You can find more information on the regional availability of the Mercedes-Benz emergency call system at: Mercedes-Benz emergency call system
If no emergency call is available due to a technical problem in the vehicle, the red SOS NOT READY message appears in the multifunction display of the instrument cluster or in the media display and the red LED indicator lights up.