Im having to sell my dear A8 4.0 TDI and I want to check that everything works, I have had the second key upstairs in a drawer for 3 years but when I try it it doesnt work, even though I know theres a good battery in it.
Is there something you have to do to get it to pair with the car again? Or will it not work if the other one in near or something?

Any help greatly appreciated.