307 Practical hints
Unlocking/locking in an emergency
Changing batteries in the SmartKey
If the batteries in the SmartKey are 
discharged, the vehicle can no longer be 
locked or unlocked. It is recommended to 
have the batteries replaced at an 
authorized Mercedes-Benz Center.
Batteries contain materials that can harm 
the environment if disposed of improperly. 
Recycling of batteries is the preferred 
method of disposal. Many states require 
sellers of batteries to accept old batteries 
for recycling.1Mechanical key
2Battery compartment
Replacement batteries: Lithium, type 
CR 2025 or equivalent.
Remove mechanical key1 
(page 305).
Insert mechanical key1 in side 
opening and push grey slide.
Battery compartment2 is unlatched.
Pull battery compartment2 out of the 
SmartKey housing in direction of 
arrow.
3Battery
4Contact spring
Remove the batteries.
Using a lint-free cloth, insert new 
batteries under contact spring with the 
plus (+) side facing up. 
Return battery compartment2 into 
housing until it locks into place.
Warning!
G
Keep the batteries out of reach of children.
If a battery is swallowed, seek medical help 
immediately.
iWhen changing batteries, always 
replace both batteries.
The required replacement batteries are 
available at any Mercedes-Benz 
Center.