Audi Repair: Automatic Door Lock, 2003 audi a6, audi a6

Question
I have a 2003 Audi A6 and the automatic door lock (when you drive over a certain speed they lock and then unlock with key removal) doesn't always want to work. It'll go in spurts of 3 or 4 weeks working then suddenly stop. Any suggestions for fixing this?

Answer
Does the central locking work OK otherwise?  This could be a speed sensor, or the central locking module itself.  If it is an intermittent problem like this, it is more than likely a loose connection, but the trick will be finding it...  Good Luck,  Jan