security horn on 2006 beetle goes off without any disturbance ??

Actually, there will not be any faulty codes because the security system is, technically, working fine. A dealership of VW mechanic shop will be able to determine which module is bad by individually testing them and by the log of when the security system was last activated. The door and trunk sensors are the most common to fail, though there are other modules that can go bad. If you leave your car unlocked, the car will still secure itself with passive standby, but not with any sound. Meaning, someone can open your door and nothing will make noise, but they still can't start the car (unless they're uber savvy or have your key). So basically what the other guy said, plus the added quippet of: don't slam your doors! GL!