W204 Key Issue - Spare suddenly won't work

W204 Key Issue - Spare suddenly won't work

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joropug

Original Poster:

2,669 posts

194 months

Wednesday 2nd December 2020
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2013 C class - Normal mercedes key not keyless entry or start.

I went to use the spare key today and it wouldn't unlock the car, once opened with the other key i also found it wouldn't start the car, turning it does nothing at all.

The battery didn't seem flat (red LED lights on press) but changed it anyway. Hasn't resolved.

The key has been in a safe for a year, it was used by the garage during service at least once in my ownership and the blade definitely fitted the door so it's the right key (i.e. not a mix up at the garage etc ).

So has anyone experienced this and more importantly know how to reprogram it ?