Reducing the energy consumption of the key
All vehicles: if you do not use the vehicle or a key for an extended period of time, you can reduce the energy consumption of the respective key. To do so, deactivate the key functions.
To deactivate:
press the 
button on the key twice in rapid succession. The battery check lamp of the key flashes twice briefly and lights up once.
To activate:
press any button on the key. When the vehicle is started with the key in the stowage compartment of the centre console, the key functions are automatically activated More.
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 made automatically More or manually . 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.
Messages in the multimedia system display:
SOS READY: emergency call available
SOS NOT READY: the ignition is not on or there is a malfunction with the emergency call system.
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 an emergency call is unavailable, a message to this effect also appears in the multifunction display of the instrument cluster.