Why does my Audi A2 show a warning for low coolant levels?

I recently purchased a used Audi A2 and noticed that the coolant level warning light has come on a few times. I have checked the levels and they seem to be fine. What could be causing this warning and how can I fix it?

The first thing you should do is check the sensor located in the coolant tank. Sometimes dirt or debris can get stuck in the sensor, giving an incorrect reading. If everything seems normal, it could be a faulty sensor and should be replaced.