I have been having issues with my soft close not working. Everything else is GTG including the door locks and dynamic seats. The PSE pump would not stop until it timed out. After 3-4 door closes of each door, the computer shuts down that circuit in order to save the pump thinking that there may be a leak in that circuit. The pump would run for ~15 seconds or so every time before the timer would shut it down to prevent overheating. From reading around the forum I knew that the pump was on the way out.

So I went looking for a replacement. I saw plenty of them on ebay for $500+ but they were used. The forum sponsor (mymercedesparts.com...a dealer somewhere in The South BTW) had a decent deal on a NIB OEM part for ~$700. I thought it was worth the extra $200 to get a new part so I did not have to worry about how well-used a used part was. They were easy to deal with and have pretty decent prices online for a MB dealer.

I asked the online parts guy there if the PSE pump was plug and play. He asked his service manager and was informed that it has to be programmed-in using STAR. I decided to go ahead and install it today anyway and was pleased to see the soft-close working again and noted that the pump would stop promptly in 3-4 seconds after the soft-close had pulled the door in. Everything seemed to be working OK with the new pump in place. So I pushed the pump home in the cubby inside the trunk and buttoned up everything in the trunk.

THEN I tried closing the trunk and....nothing. Neither of the buttons for closing the trunk would work nor would the switch in the driver's door. I have to open and close the trunk manually. When I press the button under the handle in the trunk lid to open the trunk it unlatches and pops up a bit but then gets sucked back down and locks in place. It will not open or close without forcing it manually.

Does the PSE pump work the winch that pulls the automatic trunk closer? Will this regain functionality if I get the PSE programmed to the car? If so, is there anyone with STAR and the know-how to program it in Southern California who would be willing to hook me up with their system and get it done for a nominal fee?

It is nice to have the doors and everything back in business. It was one of the nicer features of the car and it was worth it for me to drop the $$ on the part. I need to get the trunk closer working again though. Anyone out there who can help a brother out?

Keith

 

its plug and play.

 

OK. So anyone with any ideas as to why the auto open/close will no longer work in the trunk. It was working fine prior to installing the new PSE. It will not open with the remote, nor the buttons under the handle on the trunk, nor on the release on the driver's door.

Working fine prior to the new PSE. After installing new PSE, not working.

Keith

 

Keith,

Verify the electrical connectors at the PSE unit. The trunk switches and sensors feed directly back to the PSE unit. Cork is correct, the unit does not require any setup IF it is the correct part number for your model. I was told through my MB parts guys that there are variations in the PSE. Could it be reprogrammed? I suppose, but I do not recall seeing anything within Star DAS.

It is quite interesting to read of what happens when you unlock the trunk. The sequence should be this... PSE unlatches the trunk (which pops it up a tad), a sensor in the latch senses the unlatching, then the hydraulic pump activates and pushes the lid up. In your case though, the hydraulic pump does not seem to be activating. Lid movement (open or close) is only done with the hydraulic pump (located next to the battery).

Your sequence suggests that the logic within the PSE is incorrect for your model or a crossed wire. The fact that the hydraulic pump does not activate AND the lid latches automatically while trying to open, strongly points to the PSE, which controls the sequencing. I doubt the pneumatic lines are crossed as the hydraulic pump is energized electronically. So it's not receiving a signal.

Get the part number off the PSE unit and let's see if that is correct for your application. Now that doesn't mean the innards are correct as the case is fairly easy to open and swap parts. Not saying that's the case; just a possibility. If there is no part number, then I'd be pretty suspicious of the PSE unit. In any case, I'd also attempt a warranty exchange.

Cheers,
Jeff

 

Thanks, Jeff. Very helpful indeed.

I bought the part from a dealer in Atlanta (the forum sponsor) who did ask for my VIN to ensure that the part was indeed the correct part number. He WAS the one, however, who told me that the part was not plug and play and that it has to be programmed to the car. I did not perform a cursory inspection of the part number upon install. The part looked exactly like the one in my car and I assumed that if it did not function normally I would have to take it somewhere to have it programmed to my vehicle. I was happy to see that it did work all of the parts that it controls with the pressure/vacuum pump. But your rationale for the trunk not opening makes sense. I will have to recheck the part numbers to see if the new one is the same.

Keith

 

On my S55 I get the same issues with the trunk opening from time to time. I reset the 20Amp fuse in the rear passenger foot well and everything works fine again for a period of time. You might want to try resetting the fuse to see if it helps.

 

Perhaps the dealer was right after all, and the programming tells the PSE whether or not the car has the lid opening system...

 

Apparently, you are correct sir. They are delivered with basic programming and must be reset to accommodate cars with "extras" such as the auto-open trunk lid.

NOW I have to have the new PSE reset.

 

That is correct. Some minor coding required for the PSE pump even after the fuse pull the codes still remain "current' in the PSE control module. SDS would be best but if it works after pulling it in then it works

 

just learned something new, thanks!

 

Where in SDS can I code this?

 

2005 S500 ..... my pump was bad so I went looking and I was quoted $700 range. Talked to a few garages and decided I was going to take a chance on 'used/rebuilt'. Found a guy that had great reviews etc. He told me any PSE with code '05' or higher would work, not lower .. 05 being my model year. The code is on the side of the pump. I bought a used '08' that he rebuilt and it was plug and play as long as you replace the hoses correctly. Worked perfect. Went back and bought another to have as spare. First one cost $289 .. second one $250.
I was going to bite on the $700 pump but I gambled.

 

I'm new to this old MB stuff but my exp with those pumps is they are plug and play and have to be right one for your car. There is a sticker code on them and near the end there is a 2 digit # that correlates to year of car. Mine is an 05 and supposedly anything 05 or higher works. Not anything below 05, my year. I replaced my pump with a code 06 and everything works. I took a stab at a used on for $260 on ebay. I bought 2 actually, have a spare, both work fine. Guy I bought off rebuilds them. It was a year ago so can't help with a name.
As I said, I'm new to this and maybe just got lucky. I bought a 1 owner, 61k miles out of CA. Had it shipped to PA.
Good luck.

 

The PSe pump is 100% NOT plug and play. It must be programmed at the factory or the coding can be transferred from an old pump to a new pump.