Peugeot 4007 start stop problem

It certainly sounds like a battery issue. The start-stop system is very sensitive to voltage. Have you had the battery tested? A weak battery will cause the system to disable itself to preserve enough power for starting. The engine stalling could be related if the voltage drops too low when the system tries to restart the car. If the starter motor doesn't get enough energy, the engine might stall. Is it the original battery?

Thanks for the quick response! No, it's not the original battery, it was replaced about 4 years ago. I haven't had it tested specifically for this issue, just a general checkup last year. So, you think a battery test is the first thing I should do? Is there anything specific I should ask them to check regarding the start-stop system?

Yes, get the battery properly load-tested, specifically mentioning the start-stop issue. Ask them to check its internal resistance as well. A battery can show good voltage but still fail under load if its internal resistance is high. If the battery checks out fine, then further diagnostics will be needed, but a weak battery is the most likely culprit given the symptoms. Considering the error stored in memory and the age of the battery, replacement is likely needed.

Thanks! I took your advice and got the battery tested. As you suspected, it was heavily discharged and defective. I replaced it, which cost 290€, and now the start-stop system is working perfectly again and no more engine stalling. Appreciate the help!