Peugeot Partner engine stalling

Incorrect fuel composition, eh? That's not something you hear every day. Is your fuel economy significantly worse than before? Have you noticed any black smoke or unusual smells? You might be getting too much, or too little fuel for proper combustion.

Fuel economy hasn't really changed, and no weird smoke or smells that I've noticed. Could a dodgy sensor cause it to think there's something wrong with the fuel mixture, even if there isn't?

A faulty sensor absolutely could trigger that error, but so could an actual issue with the fuel system. Considering the symptoms, error code, and especially your mileage, I'd advise taking it to a trusted workshop. Diagnosing fuel system issues can be tricky and require specialized tools. You mentioned checking the fuel filter, which is good, but it could be something like a defective cable, or a faulty plug connection.

Took your advice and brought it in. Turns out it was a defective plug connection. Repair set me back 95€. At least it's sorted now.