Mercedes C Klasse Hybrid Keyless Entry Problem Solved

Sounds like a potential wiring fault. Have you checked the door harness where it passes from the car body into the door? It's a common spot for breaks, especially with that many kilometers.

Thanks for the suggestion. I haven't checked the harness yet. Is this something easily accessible, or would I need to remove the door panel?

It varies by model, but on yours, accessing the harness usually requires partial door panel removal. Given the error code and symptoms, it's likely a defective cable or plug connection, as you suspected. Is the effort worth it, or is a garage visit in order?

Appreciate the advice. I took it to a workshop, and you were right: it was a wiring issue with the door handle. The repair, including parts and labor, came to 95€. All is working as expected again.