To get rid of the check engine light on an Audi, it must be reset using an OBD diagnostic tool, which can be purchased at most auto parts stores. The display on the OBD diagnostic tool also will tell you what is wrong with the Audi's engine that sparked the engine light to turn on. Resetting the check engine light without going to an Audi dealer or mechanic can save you about £35, according to Audi DIY. The process is fairly easy to do in the comfort of your own garage and the tool works on all Audi models from 1996 to 2010.
Park the Audi on level ground.
Place the OBD diagnostic tool or scanner into the Audi's OBD II interface, which is located behind the hood release on the driver's side of the Audi, inside of the vehicle. Reach underneath the dashboard to get better access to the interface. The OBD II interface is also known as the diagnostic port.
Wait for the display on the tool to display the reasoning for the engine light and for the check engine light to be reset.
Remove the tool from the Audi.