Problems with the pneumatic system can cause closing assist and door lock issues.Google+
Car Problem Reports
Mercedes-Benz S500 Closing Assist/Door Lock Issues Due to Pneumatic System Problems
Mercedes-Benz S500 Problem
Average Mileage: 102,205 mi (42,000 mi - 160,000 mi)
System fails to close doors. Removing fuse will make it work again (for an unspecified time period)
Visitor, 2003 Mercedes-Benz S500, 109,400 mi
The central locking system does not work from the smartkey nor from the interior buttons. The truck will not open with they key either. I replace the 20 amp fuse in the F62 space from under the rear passenger back seat behind the light. This did not solve the problem. I can hear the pump go on and off as I press the key but does not do anything. The headrests do not go down either when pressing the release button. Not sure if its a leak or not.
Visitor, 2003 Mercedes-Benz S500
failure in pse system...remote does not open doors are trunk of car.
Visitor, 1995 Mercedes-Benz S500, 79,500 mi
Passenger door won't close. Must roll down front and back windows, close the door and use key to lock door to get windows to close fully.
Visitor, 1998 Mercedes-Benz S500, 85,000 mi
Can the Bosch Vacuum Supply Pump which assists with closing the doors and head rest be repaired or must it be replaced.
Visitor, 1999 Mercedes-Benz S500, 125,000 mi
ITS A REOCCURRING PROBLEM, A TEMPORARY FIX FOR MOST OF THE SYSTEM IS REPLACING THE FUSE IF THE PROBLEM CONTINUES FOR ONE ITEM AND NOT THE OTHERS (I.E. THE TRUNK STILL DOESN'T WORK BUT THE DOORS DO.) THEN ITS USUALLY PRESSURIZATION ISSUE AND EVEN THAT CAN BE A SIMPLE FIX IF YOU CAN FIND THE AIR LEAK.