Citan check engine light and engine knock

I had similar car problems with my Citan a while ago. Check engine light was on, rough idling. Turned out to be a faulty knock sensor. Have you checked the cable and plug connection? That's often the culprit.

Thanks for the info. Where exactly is the knock sensor located? And how can I check the cable and plug myself?

On my engine, it's near the engine block, but location can vary a bit. Visually inspect the cable for damage, like cracks or breaks. Unplug it and check for corrosion on the pins. If you're not comfortable doing that, a workshop can sort it out, it shouldn't be too expensive. I guess around 95€.

Thanks for the advice. I checked the cable, it looked fine to me. So I brought it to a workshop. Indeed, the knock sensor was defective, caused the warning light to appear and fuel consumption increased. They replaced the component. Now everything runs smoothly again.