A fault code LN2 appears in the mileage indicator when I start the car. What does it mean?

 

its not a fault code, its a service indicator light, it should go off after a few seconds or you can hold down the mileage button to turn it off, not sure if it applies to your model year but theres a DIY on audidiy.com to turn it off. or you can go to the dealer, its not really a problem, just an annoyance dont worry about it.