GLA immobilizer woes Engine wont stay running

Sounds frustrating. I once had a similar experience with my GLA, though I can't recall the exact error code. It also involved the car immobilizer. Did you try the spare key? Sometimes it's just a faulty transponder in the key. Also, is the remote start working? Before jumping to key programming, you might want to check the car electronics related to the immobilizer system, perhaps a loose connection. But honestly, it sounds like a key issue.

I did try the spare key, with the same result. The remote start isn't an option on my car. When you say check the car electronics, where exactly should I be looking? I'm not particularly experienced with that side of things.

Right, both keys failing points to it maybe not just being the key itself. Honestly, tracing car electronics issues can be tricky without the right tools. It could be the immobilizer module itself, or the wiring harness leading to it. But without proper diagnostic equipment, you might just be chasing ghosts. The best course of action would be to take it to a workshop with experience in Mercedes key programming and immobilizer systems. They can pinpoint the fault and reprogram the key if necessary. Cheaper than replacing random components. Hopefully it is just key related.

I appreciate the advice. I took it to a workshop, and they confirmed the key programming was incorrect. They recoded it, and it's working fine now. Repair cost was 45€. Seems like a reasonable price.