EQC immobilizer issue

I had a similar issue with my EQC, although I can't recall the exact mileage. The symptoms you describe match my experience. The security light was a constant companion. Did you try the spare key? Does that behave the same way? Also, have you checked the battery voltage? A low voltage can sometimes cause issues with the immobilizer and the key signal. It might be worth checking the error codes to see if they give you a clue about the specific immobilizer module involved. Is the anti-theft system engaging properly otherwise? Are you able to lock and unlock the car remotely?

Good shout on the spare key, tried it, same issue. Battery voltage seems fine according to my multimeter. As for the error codes, it's flagging up a key authentication problem. The central locking works fine. Everything seems normal, except the car won't stay running. What was the solution in your case? Key programming gone awry?

Yeah, sounds like the same gremlin. Given the error codes and the spare key behaving the same, it points to a key programming issue or a fault in the immobilizer system itself. I spent ages fiddling, checking connections, and pulling my hair out. In the end, I bit the bullet and took it to the workshop. They recoded the key, and that sorted it. Cost next to nothing. I wouldn't advise messing with the immobilizer system yourself unless you have the proper diagnostic tools and know what you're doing.

Appreciate the insight. Sounds like I'm chasing a ghost without the right gear. I'll book it in for key programming. At least I know what to expect now. Thanks for the help.