My '96 was that way when I got it. The cylinder turned, but behind it there was nothing.

There was a small pin that sheared, connecting the cylinder plug to the shaft that turned the lock. I replaced it with a small split pin from the hardware store.

Remove the lock assembly from the door -- one allen-head bolt, hidden behind the weatherstripping. I don't remember if it's possible to drop the shaft into the door when you remove the lock assembly, so proceed accordingly.