Focus oil pressure warning light

Oil contamination can cause those symptoms. What does the oil look like? Is it sludgy or a different color? When did you last change the oil?

The oil looks darker than it should, almost black. I admit the last oil change was longer ago than it should have been. Could that really be the cause, or could it be something else?

Yeah, skipping the oil change is probably it. Diesel engines contaminate oil more easily. Because of the color and the late service, it's affecting your oil pressure. Get it checked ASAP to avoid more damage.

I took it to the workshop, and the oil contamination from the late service was the problem. An oil and filter change for 165€ seems to have fixed it!