Model MB E430 1999. I have not changed a battery or done any electrical work on car for 1 year. Recently the radio, when turned on goes to the station then "CODE ?" appearson the radio, the after 15 seconds or so it goes to the previous station and the operation repeats. If I enter the code the radio works perfectly until I turn it off. Then the same problem appears. I would quess a floating short. Any Ideas. This is my first post