C70 check engine light and stalling

That's a tricky one. Incorrect fuel composition errors can be a pain. Have you noticed any changes in fuel economy or any unusual engine knock recently? Also, where do you usually get your fuel from? It might be worth trying a different station to rule out fuel quality issues.

Fuel economy seems normal, and I haven't heard any knocking. I usually fill up at the same station, but I'll try a different one like you suggested. If it's not the fuel itself, could a defective cable or plug connection cause this?

It's possible. A faulty connection to a sensor in the fuel system could definitely throw off the readings and trigger that error. Given the symptoms, and the fact that you've tried the basics, it might be time to have a workshop take a look. They'll be able to properly diagnose the electrical connections and fuel system components.

Appreciate the advice! I took it to a local shop, and you were spot on. It turned out to be a defective cable connection, which they fixed for 95€. Runs perfectly now!