Spare key not working

[Willbiker]

Hi All

I recently purchase a S205 and the spare key supplied doesn't open the car or engage the ignition. The key looks like it has never been used. Battery changed, red light on key illuminating ok. A locksmith told me that Mercedes keys 'don't just loose their programming', is this true?. The physical keys look identical so I'm confident it is the original.

I have taken the covers of both keys to compare, is there some kind of id or serial number that both keys should have displayed to show that they are mapped to the same car?

Has anyone experienced this issue before and can advise me on what the issue might be?

thanks in advance

 

[KillerHERTZ]

Could be that the previous owner lost/damaged one key, bought another spare off eBay and it was never programmed. Then, sold with '2 keys'.

 

[Bobby Dazzler]

It could be a key for a different car, or even a blank. Does the removable key blade lock and unlock the car manually?