Key opens doors but fails to start engine

I previously asked about my car that had been starting fine but when I tried to use spare key it would not start. I called out breakdown service who diagnosed that the spare key was at fault, he thought that it had not been programmed with the immobiliser. I did not realise that my V reg MX5 had chips in each key. Is the breakdown man right? If so, how do I get the key programmed?

You replied that the battery will have died and the key will have lost its code.

BUT NEITHER OF MY KEYS HAVE BATTERIES IN THEM!

Asked on 2 April 2012 by smiler6996

Answered by Honest John
Maybe it has a chip that does not require a battery and that has lost its code somehow, possibly from not having been used.
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