To test the oxygen sensor, you will need a scan tool which Audi and aftermarket suppliers offer. Audi special tool 3337 is required to remove and install the oxygen sensor to avoid damaging the sensor. When putting the oxygen sensor in, you want to use a high temperature anti-seize that contains no silicone that is further marked "safe for oxygen sensors" (Audi part# G052 112 A3). Part numbers for Audi are for reference only. Please check with your Audi Parts Department or aftermarket parts specialist for the latest parts information. Moreover, anti-seize compound must not enter slots on oxygen sensor body.