Replacing the key battery
DANGER Serious damage to health caused by swallowing batteries
Batteries contain toxic and corrosive substances. Swallowing batteries may cause serious damage to health.
There is a risk of fatal injury.
Keep batteries out of the reach of children.
If batteries are swallowed, seek medical attention immediately.
ENVIRONMENTAL NOTE Environmental damage due to improper disposal of batteries
Batteries contain pollutants. It is illegal to dispose of them with the household rubbish.
Dispose of batteries in an environmentally responsible manner. Take discharged batteries to a qualified specialist workshop or to a collection point for used batteries. Requirements:
You require a CR2025 3 V cell battery.
Mercedes-Benz recommends that you have the battery replaced at a qualified specialist workshop.
Remove the emergency key More.
Press emergency key 
into the opening in the key in the direction of the arrow until battery compartment cover 
opens. When doing so, do not hold battery compartment cover shut.
into the opening in the key in the direction of the arrow until battery compartment cover opens. When doing so, do not hold battery compartment cover shut. Remove battery compartment cover .
. Repeatedly tap the key against your palm until battery 
falls out of the key.
falls out of the key. Insert the new battery with the positive pole facing upwards. Use a lint-free cloth to do so.
Make sure that the surface of the battery is free of lint, grease and other impurities.
Insert the front tabs of battery compartment cover into the housing and then press to close it.
into the housing and then press to close it. Insert emergency key into the key.
into the key.