How can I diagnose and fix a malfunctioning oxygen sensor in my Audi A2?

I've noticed that my car's oxygen sensor isn't functioning properly, causing my fuel efficiency to decrease. How can I accurately diagnose the issue and fix it myself?

First, use a diagnostic tool to check for any error codes related to the oxygen sensor. If there are none, test the voltage and resistance of the sensor with a multimeter to determine if it's functioning within the correct range.

If the oxygen sensor is faulty, it will need to be replaced. Make sure to purchase one that is compatible with your Audi A2 model for best results. Consider also cleaning the sensor with specialized cleaner, as often buildup can cause issues.

In addition to the sensor itself, it may be beneficial to also replace the oxygen sensor's wiring and connectors. This can help ensure a better connection and prevent future malfunctions.