Audi Downstream Oxygen Sensor – Denso

It reports how rich or lean the exhaust is, and the engine computer adjusts fuel delivery in response. A faulty sensor can make the engine run too rich or too lean.

A check-engine light with oxygen-sensor or fuel-trim codes, poorer fuel economy, rough idle, or a failed emissions test. Exhaust leaks near the sensor can cause similar codes, so check for those too.

Sensors are specific to their position: upstream (before the catalytic converter) or downstream (after it), and on V engines, bank 1 or bank 2. The fault code usually identifies the position; check the product details for the position this sensor fits.

Usually, yes, using an oxygen-sensor socket. Many new sensors come with anti-seize already on the threads; if not, use a sensor-safe compound only on the threads, and keep it off the sensor tip.

Compare the part numbers listed on this page with the number on your old part or in your vehicle's parts catalog, and check the fitment information. If you are unsure, contact us with your VIN before ordering.