There's only a lock actuator and linkage. If the actuator is moving in and out (maybe the noise you heard), but the door doesn't lock/unlock, the linkage could be the problem. Can you "manually" move the linkage and lock/unlock the door? If you move the linkage and the door still doesn't unlock, it's most likely the latch ass'y itself. Of course all of this is assuming that the linkage is intact.