You can try a laser cleaning disc but I've never had much luck with them. Use the type that you add a drop of cleaning chemical to the tiny brushes. If it has to be removed for repair, let the dealer do it so they are responsible for all of the problems that will follow. Volkswagen is extremely customer unfriendly in this area and along with GM has figured out how to separate you from your money after the sale. If you don't know the secret code for your radio, it will never play again once it is unplugged or the battery is disconnected. Not sure how that design benefits the owner but it sure makes the manufacturer a lot of money.