The pnuematic system pump (PSE computer) has different "jobs" which including door locks, back-up assist (depending on your model), headrest fold-down (rear seat), ortho-seats, retractable trunk handle. This is the pump that is located under the passenger rear seat. (This is what you are calling the motor.)

Remember, the PSE pump DOES not control closure assist - door or trunk. Closure assist is controlled by a separate pump located in the trunk next to radio amp on the driver’s side.

By disconnecting the battery or resetting the fuse for the PSE Pump, you can accomplish a reboot of the pump. I cant remember if this is fuse # 9 or # 3 .. check your diagram) By removing the fuse and reinserting the fuse, after waiting a few seconds you can reset the pump sometimes providing a temporary fix to your PSE pump problem. (kind of like reboot a computer) If the pump is working you will also hear a humming noise coming from under the rear seat location when the system is activated.

As a side note: If the system senses a leak it also shuts down, but after resetting you should hear it run. There is a 10 second shut down in locking and a 60 sec shut down in consumers. I would try the keys since they control the pump directly.

PSE pump failure is common in our model of MB. I think the dealer part cost is about $750. If you’re mechanically inclined (DIYer) you can find a replacement pump and install it yourself. FYI.. MB has moved to “universal PSE” pump, so you may need additional hose connectors to complete your replacement, but since you have an 1993, you will need the ddtional hose connectors for replacement. (Your PSE pump is located under the rear seat on the passenger side.)

I'm guessing the frequency of the "resets" will become more bothersome as the motor in the PSE pump continues to fail. I've heard of people attempting to rebuild the motors in the pump, but finding parts seems to be impossible.

Russell

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Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML