Had a similar prob with my 1993 Passat Estate. you need to remove the plastic door trim on the inside of the tailgate(many screws and pastic anchors on mine). This will give you access to the solenoid,operating arm and lock.After ample lubrication(lock not you) and working of the mechanisms,lock should operate. I fitted one end of a piece of string to the lock operating arm and the other end I coiled up in the tail light cluster access panel so that i could open tailgate if the solenoid failed closed. Good Luck
Willie, January 2007