at http://bbs.wenxuecity.com/auto/365132.html
The power door lock is similar as power window. It is a DC motor connected with different direction so that it can lock/unlock. If you can unlock all doors, but can not lock other 3 doors, it is like the wire/swtich borken for the lock path. It could be a soldering point broken. Check the common wires to other 3 door and soldering point.
Get a reapir manual, you should be able to figureout where to look at.
