What are the common causes of a check engine light in Audi A4?

My check engine light has come on in my Audi A4. What could be causing it and how can I fix it?

The most common cause for a check engine light in an Audi A4 is a faulty oxygen sensor. However, it could also be caused by a loose gas cap, a failing catalytic converter, or a problem with the engine's computer system. My advice would be to take your car to a trusted mechanic to have it diagnosed and properly fixed.

Another possibility for the check engine light is a dirty or clogged air filter. This can cause the engine to run less efficiently and trigger the light. I would recommend checking and replacing your air filter if it is dirty or clogged.

In some cases, a simple fix for the check engine light is to tighten the gas cap. If the cap is loose or not sealed properly, it can cause the light to come on. Try tightening the cap and see if the light goes off before taking your car in for service.