What's the 00473 Audi fault code?

The 00473 Audi fault code means 00473 - Control Module for Elect. Park/Hand Brake (J540): No Signal/Communication. What this means is that the parking or hand brake is not in connection with the main computer of the car. This could be a bad wire or a burnt-out fuse, but in short, the brake will not work, as the signal to apply it will not be sent. While You can technically ignore this, it is not good to not have a brake on hand, so You are best to take it into the shop and have them take a look at it. That assumes it is not a bad fuse, which can be fixed at home very simple and for cheap.