Mercedes-Benz 2015 M-Class Operator's Manual page 86

SmartKey
84
Repeatedly tap the SmartKey against your
X
palm until battery = falls out.
Insert the new battery with the positive ter-
X
minal facing upwards. Use a lint-free cloth
to do so.
Make sure that the surface of the battery is
X
free of lint, grease and other contaminants.
Insert the front tabs of battery compart-
X
ment cover : into the housing first and
then press to close it.
Insert mechanical key ; into the Smart-
X
Key.
Check the function of all SmartKey buttons
X
on the vehicle.