If the Mercedes S-class electronic key (W221) has stopped working, it is likely to change the battery in the key chain. To do this:
- Buy the button battery battery CR 2025 on 3 V.
- Move the latch on the key chain to the right and pull the emergency key ("beak") out of a keychain.
- Put the emergency key in the hole in the key hole and push until the battery lid opens.
- Remove the lid and shake the battery out of the key.
- Put a new battery, pre-wipe it with an unorthodox cloth.
- Let' s get the logs back.
