How to Replace an Audi 4.2 Oxygen Sensor

1. Allow the Audi to cool for 15 minutes. The oxygen sensor and surrounding components will still be slightly warm, but this is ideal for replacing the oxygen sensor.
2. Open the hood of the Audi and locate the oxygen sensor. The oxygen sensor is located on the left side of the Audi 4.2 exhaust manifold. You can easily identify the oxygen sensor as it's the only sensor located on the left side of the manifold. The sensor looks like a metal cylinder the size of your little finger.
3. Use a socket wrench and oxygen sensor socket to loosen and remove the oxygen sensor. If preferred, you can use a 22mm socket instead of a oxygen sensor socket. Turn the socket wrench counter-clockwise to loosen the sensor. Remove the sensor by pulling it out of place once it's loose enough.
4. Insert the new oxygen sensor into place and plug the sensor into the connector located on the manifold. Your new O2 sensor is now installed.