Citroen C3 Start Stop Problem

I had a similar issue with my 2018 BMW 3 series, also diesel. The start-stop malfunctioned intermittently, and the error memory indicated a low battery charge. Is your battery original? Have you checked the voltage when the engine is off and under load? The system is very sensitive to voltage drops.

The battery is original. I haven't checked voltage yet. If it is the battery, is a replacement my only option?

Unfortunately, yes, a replacement was the only permanent fix in my situation. After several diagnostic procedures, it became apparent that one of the battery cells started failing. I suggest having it professionally tested to confirm the diagnosis, as a faulty sensor could also produce similar symptoms. After that, if it is indeed the battery, replacing it is the correct path.

Thanks. I'll get it tested. It ended up being the battery, as suspected. 290€ to fix.