What is the function of the lambda sensor in an Audi 80?

I recently noticed a warning light on my Audi 80 indicating an issue with the lambda sensor. Can you explain what it does and why it is important?

The lambda sensor, also known as the oxygen sensor, measures the amount of oxygen in the exhaust system and sends this information to the vehicle's computer. This data is used to adjust the air/fuel mixture, which in turn affects engine performance and emissions.

If the lambda sensor is malfunctioning or has failed, it can cause various issues such as increased fuel consumption, engine misfires, and failed emissions tests. It is important to address any warning lights related to the lambda sensor and get it replaced if necessary.

To check if the lambda sensor is functioning properly, you can use a diagnostic tool to read the sensor's voltage output. This should be between 0.1 to 0.9 volts with the engine idling. If it is outside of this range, the sensor may need to be replaced.