leaving the key in the slot drains the programming out of the key....it will need to be reprogammed...when this happens on E class cars it burns the eis module as well...i haven't seen it do this on a c230 before....NEVER leave the key in the ignition on these cars for an extended period....there is a green programming key the dealer uses to initiate reprogramming your key...hopefully this is all that you will need to have done...if the key won't take reprogramming it might have to be replaced...hopefully the eis module hasn't been damaged....
