Fiesta immobilizer fault

I had a similar problem with my Fiesta. The anti-theft system went haywire and the car wouldn't recognize the key. Does the security light flash when you try to start it? It might be a faulty key signal.

Yes, the security light does flash intermittently during the attempted start. Was your issue definitively related to the key programming itself, or could it be a broader issue with the immobilizer system?

For me, it turned out to be a key issue. The signal wasn't being properly read by the ignition control. Best to get it checked by a workshop with the appropriate diagnostics equipment.

Thank you for the advice. I had the key reprogrammed at a workshop, and the issue is now resolved. The repair cost was 45€.