Skoda Octavia diesel engine issue

It sounds like your crankcase ventilation valve is indeed the culprit. The symptoms you describe – check engine light, reduced power, and smoke – are all classic signs. The crankcase ventilation system is like a car's lungs, preventing pressure buildup by recirculating gases. A faulty valve can cause all sorts of problems, including those you're experiencing. Have you checked the hoses connected to the valve for cracks or blockages? These can sometimes cause similar issues. Also, what does the smoke smell like? Is it oily or more like fuel?

Thank you for your input. I have visually inspected the hoses, and they appear to be intact without any obvious cracks or blockages. The smoke smells more oily than like fuel. Could a faulty valve cause the engine to burn oil, even with the low mileage?

The oily smell definitely points towards the crankcase ventilation system. And yes, a faulty valve can absolutely lead to oil consumption, even with relatively low mileage. Think of it like this: if the valve isn't regulating pressure properly, it can force oil past the piston rings and into the combustion chamber, resulting in it being burned and producing that oily smoke. While you've checked the hoses, the valve itself might be internally damaged or clogged. Considering the symptoms and the oily smoke, I'd recommend taking it to a trusted workshop for a proper diagnosis and replacement of the valve. It’s better to address this sooner rather than later to prevent potential further engine damage.

I followed the advice and had the crankcase ventilation valve replaced at a workshop. The total cost came to 360€. The car is now running smoothly again and the check engine light is off. I appreciate the help.