Mercedes GLC Immobilizer Problem Solved

Your symptoms sound like an issue I had with my BMW 5 series. Though different makes, car electronics and immobilizer systems can act similarly. My engine would either not start, or start and cut out. The security light also flashed. Have you tried a spare key? Also, is the key fob battery fully charged? A weak battery can cause communication issues with the immobilizer.

Thanks for sharing. I tried the spare key, but the problem is the same. I also replaced the batteries in both fobs, but it didn't help. In your BMW, was the problem just key programming, or did it involve other parts of the ignition control system or immobilizer?

My issue was corrupted data in the immobilizer module, which required reprogramming the keys and the module. Other ignition control components could be at fault, but your symptoms point to an immobilizer fault from key programming. Since you tried the spare key and replaced the batteries, I'd suggest seeing a qualified technician with the right diagnostic tools to check the car electronics. A workshop visit might be needed.

I appreciate your insights. The dealer confirmed it was a key programming issue. Reprogramming the key for 45€ fixed it. Thank you again for your assistance.