Renault Scenic Start Stop Failure

I had a similar issue with my Scenic. If the battery is heavily discharged or defective, the start-stop system will be disabled to prevent the starter motor from being excessively strained. Have you checked the battery's voltage and condition? A drop in voltage can certainly trigger the symptoms you described.

Voltage drop, huh? How would I even test that properly?

You would need a multimeter to measure the battery voltage. However, given the symptoms and the potential for further electrical issues, I would strongly suggest taking it to a qualified workshop. They can perform a proper diagnostic test and confirm whether the battery is indeed the culprit. Replacing it yourself might not resolve underlying issues.

Thanks! Workshop it is. They reckon the battery was knackered; new one fitted, cost about 290€. Start-stop's back in action!