Eco mode engine failure 508

Hello, I am using 2012 Peugeot 508. Today, I started to get an engine failure warning while I was driving at low speed. I usually use Eco mode off. When the fault screen came, eco mode was automatically activated. When the vehicle stops, it stops due to eco mode. But it doesn't work when I press the gas, it wants to contact again. Has anything happened to him before? Can you share your experiences?

I changed the alternator tensioner and the problem was solved.