Is there a fuse to control the door locks and cabin controls on Mercedes 2000 s430?

Are all the door locks inop? sounds like you might have a PSE problem, that is your vacuum pump, the door locks on your car are vacuum operated, the fuse for that pump should be in the rear fuse box I belive. rear fuse box is located below the rear passengers seat. you have to remove the plastic cover which houses the little light, just unclips from the top. then you can check all the fuses in there and see if one is blown, otherwise you might have a bad vacuum pump.