Seat Altea Diesel Immobilizer Problem

The symptoms you describe indicate a potential issue with the car immobilizer system. Does the security light behave erratically? I experienced a similar problem with my Opel a few years back. Was the key recently damaged or has the car battery been disconnected?

Security light seems normal, no recent damage to the key and battery has not been disconnected. What was the issue with your Opel?

In my case, the car immobilizer was triggered by a faulty transponder in the key. This prevented the ignition control system from authorizing the engine start. If the security light is not showing any abnormalities, it may still be a key issue. The error stored in the memory suggests that the anti-theft system is active. I strongly suggest consulting a qualified technician to reprogram the key or diagnose the immobilizer system further.

You were spot on. Took it to a garage, they reprogrammed the key for 45€. Sorted. Cheers for the steer!