How do you replace the battery in a 2004 Passat?

Do you have the radio code first of all? otherwise it won't work later. Take off the ground cable first , then the positive (red). VW batteries have clamps on the bottom that must be unbolted. Rinse tray and clamps with baking soda water if corroded. Replace negative clamp last to avoid shorting battery by mistake.Reenter your radio antitheft code to make it work again.