Well I stored the tire pressures and went for a 45 minute drive. I still have tire pressure malfunction. I know the sensors are the original, probably 5 years old. Should I just start by replacing the sensors? With my current MMI version I am able to turn of TPMS. I have read that with newer versions I cannot do this. Since the TPMS is not working will I be getting annoying errors left and right if I do the MMI upgrade?

 

The sensors are not cheap, like $150-$300 a wheel depending on which sensor is in there. I would have the dealer do the diagnosis procedure, that way once they diagnose it and it goes wrong after they fix it they are liable to fix it for good.
As for the up-date i have no way of knowing that, now if i owned the A8, i would just turn off the TPMS system and say the hell with it. I mean, just do a walk around your car every once and a while and you will notice if a wheel is low on pressure, I HATE the TPMS system.