Why is my Audi A4's check engine light on?

I just bought an Audi A4 and the check engine light came on. What could be the reason and how can I fix it?

It's important to address the check engine light as soon as possible. It could be a minor issue, like a loose gas cap, but it could also indicate a more serious problem. I suggest taking your car to a certified mechanic.

One common cause of a check engine light is a faulty oxygen sensor. You may notice a decrease in fuel efficiency or engine performance. Get it checked and replaced if necessary.