Renault Scenic check engine light and fuel consumption

Greetings! An illuminated check engine light alongside reduced power and increased fuel consumption indeed suggests an issue with the exhaust system. Do you observe any unusual noises emanating from beneath the vehicle, particularly during cold starts?

Thanks for the quick reply! No, I haven't noticed any unusual noises. Could it still be a leak even without the noise?

Indeed, a leak might exist without producing noticeable sounds, particularly if it is small or located in a less exposed segment of the exhaust architecture. Given the confluence of symptoms you've described, coupled with the age of the vehicle, a professional diagnostic assessment is prudent to ascertain the precise nature of the fault. I advise a qualified workshop visit.

Thank you! I took it to a workshop, and you were right. It was a faulty exhaust temperature sensor caused by a small leak. The repair cost me 265€, including the sensor replacement and fixing the leak. All is well now.