Can you give us some 'history' here?
Is this the original PSE module, or have you just changed it for another?
Was this working OK, and then recently failed.

Of course the PSE pump is supposed to run until the system is up to pressure, and then turn itself off. I guess that the pressure sensor is inside the unit, as I cannot see one elsewhere. It could be that this sensor is turning off the pump too soon.

Could this be an issue with your remote key? Have you tried your spare?

How about the fuel filler flap. Is that affected? Do you have the Multicontour seat feature?

Lots of questions here.

 

Thanks for a quick response, keyhole --

* I believe it's the original PSE; I've owned the car for about 8 months and everything worked without issue until about 3 weeks ago.
* No spare key; car only came with one.
* Fuel filler flap works OK.
* No multicontour seats.

The PSE runs for 15-20 seconds before 'timing out', very similar to action others have described.

Hope that helps!

 

Correction - the fuel filler flap does NOT work. But as I mentioned earlier, only the trunk works just fine with remote or manually.

When I hear the PSE pump trying to work, I can tell a distinct difference in the sound whether I'm trying to 'lock' or 'unlock' everything.

 

As you realize, this 'hybrid' design on your W208 (and other MBs of that era) uses both electric and pneumatics to operate several systems - the most important of which is the door locks.

I believe (but must double-check) that vacuum is used for the locking actuations, and pressure is used for unlocking. Because the locks must operate when the car is parked, a reservoir/ accumulator is also included. This is also located in the trunk. All the actuator initiation from the Central Locking system is done electrically.

So you can appreciate that you have a 'dog's breakfast' of systems here!

I would try to eliminate the pneumatic operations first. Can you move the PSE unit in the trunk far enough that all the pneumatic line outputs can be examined with the power on?

If so, using the WIS drawing below, check that you get pressure/vacuum at the 'ports' shown when the appropriate switch operates. Do all the functions listed. Without a gauge as shown on the WIS drawing, you will have to guess if the pressure/vacuum at the port is enough to operate the item. If the pressure produced is very low, it might explain why only the trunk lock is working.

Finally, there is the issue of 'coding' for each PSE control module. This is determined according to the build of each car, i.e. the multi-contour seat outlet is not pressurized if that feature is not there. I assume that a blanking plug is used. Also there are 'options' on how 'automatic' door locking is required. This is as shown on the WIS diagram. I do not think that you have a coding problem, but you may as well be aware that it exists, if a replacement is ever used. Coding can only be done with MB diagnostic kit.

 

A 'dog's breakfast' of systems ... still chuckling at that one!

What you've described begins to lead me to the reservoir/accumulator. I'll pull the PSE and go buy a gauge to verify those pressures at the various hoses. Will a My-T-Vac or something similar work for me here?

* If pressure is low, is it likely the reservoir/accumulator?
* Does this look like the "double-balloon" thingy in Drawing #1?
* Is this a separate device from the black PSE unit itself?
* If separate, does connector #2 (in Drawing #2) lead to it?
* Finally, is this something I can buy (instead of an entire PSE pump) and install myself?

I'm aware of the potential coding requirements, so if I have to buy an entire PSE pump, I'll have a service tech install it.

Keyhole, I've seen in many places on the forum where you've been most helpful for so many others. I hope to be able to 'pay it forward' someday!

Thank you again for your help here. I'll post back and let everyone know how it all works out.

 

After digging into my WIS, I have come to the conclusion that the pneumatic reservoir that I referred to earlier is only used if the multi-contour seat (MCS) feature is fitted. Not for the basic central locking system. So I guess that we can ignore that idea now.

The EPC drawing below shows all the PSE connections. It shows the 2 couplings (#70) that fit to the door actuators (not numbered here), the filler flap element (#5) and the trunk lid element (#35). No reservoir is shown, but I do not know what (blanked out) items #15, 25 & 20 are.

So to answer your questions:

1. I think not
2. No, that is just for MB testing.
3. For a MCS system - yes. Here - no.
4. No those are electrical connectors. The MCS reservoir is just a tank.
5. I don't think that you will need this.

Thanks for your comment. It's always rewarding to get some feedback if/when a problem is solved.

 

Hmmm ... I'll keep tinkering a bit more, than likely spring for the PSE module.

Any thoughts - pro or con - on the Ebay ones for $150 vs $700-800 for dealer plus installation?

 

Can I trouble you one more time, Keyhole?

I'll do the vacuum test you suggested with a gauge ... you mentioned that, although the PSE is running, the pressure may be too low to operate the locks, etc ...

* Do you know what pressure is considered 'too low', and
* Is this a fixable problem or does it indicate that the PSE is about shot and simply needs replacement?

Again, many thanks for all your guidance! :bowdown:

 

There is a mass of information in the WIS on testing the pneumatics & electrics of the PSE control module. It does require an MB test box, but the values are useful.

Here is a segment of information for a pneumatic test of the door locks. Section 4 on page 1 is the closest I can see for your situation.

It shows that the design pressure from the PSE should be 600 mbar, and it should drop by no more than 25 mbar in one minute.

So that is the target for the unit. If the pressure is OK and the locks still don't work, it suggests a bad actuator or a leak in the lines. Of course there is also the electrical side to consider.

If the pressure is not OK, I guess that the pump is toast. Can you find a gauge that measures very low pressure, i.e., less than 1 atmosphere?

I believe that this MB central locking design is 'over-engineering' at its worst. Fortunately it is all tidied up on the W209 class and later models.

I did eventually find the drawing showing the reservoir for the MCS feature. It is for saving a vacuum. It has left me wondering how the regular PSE system works without a reservoir. I mean, how can the doors be opened before the pressure/vacuum has been generated, if the PSE pump only comes on when the ignition is on?

 

I'm in the home stretch of this thing I think. I'll post how it all works out.

But your very last sentence is intriguing "the PSE pump only comes on when the ignition is on." ... I hear my pump working when use the key fob remotely.

 

Aah...you may be right there.

I have assumed that the ignition key turns on the PSE pump. Maybe it is the electrical side of the central locking system that does that job. I'll have to check the circuit further.

 

The only thing nagging at me before I buy a PSE module is that I've pulled the module TWICE -- disconnecting lines for visual inspection and air flow operability -- and after I've reconnected and reassembled, all systems works perfectly for a few cycles (the first time, it worked three times then failed).

Second time, I actually pulled the housing off the module and primitively "jiggled" the hose connections amidst components in there, and put it all back. This time, the system worked 6 or 7 times in a row before failing. I really thought I had fixed until that point.

I don't see that I have much to lose by repeating the procedure one more time - and this time, really focus on those hose connections, and try to secure them all snugly with a dot of super glue. I suppose if it doesn't work, I'm buying that PSE module anyway.

Any final thoughts / suggestions before I try this tomorrow? Either way, I'll post how it all turns out.

 

In your situation, I wold be tempted to 'open up the box' - if you can. Maybe you can lubricate the pump? Did you check the pressure produced?

 

Ended up having to replace the PSE module. Indy mechanic confirmed that I had done everything possible regarding troubleshooting, so I can take some measure of satisfaction in that. Cost was a bit less than I had anticipated ($800 inc. installation and reprogramming), so that helps too.

Keyhole, thanks again for your advice and time required to research, post, etc. regarding my problem. Please know that you have inspired me to become more proactive in 'paying it forward' when it comes to knowledge and experience I'm gathering along the way here!

 

My problem, in the 2001 clk55 amg, is that the multicontour seats are the only malfunctioning PSE pump driven system. If the seats are driven by positive pressure, why is the connected reservoir for maintaining vacuum?

 

General thought when replacing a PSE unit...If you think you have a bad PSE motor, this might be obvious but maybe someone out there didn't think of the following: In general when replacing a PSE with a bad motor on a car that has contour seats, you need to get the New PSE -or- donor PSE programmed assuming the used donor PSE didn't come off a car with contour seats. This is a chunk of $$$ you shouldn't spend! But if you save your original PSE unit with the bad motor, the circuit board is still correctly programmed for your contour seats. So why not swap out the motor from the donor PSE into your original PSE unit? This way your contour seats will still work after reinstall. You can usually find a donor pse that matches your part number on ebay in the $45-75 range. If you don't want to solder the motor's 2 wires to thee circuit board, then although i am not an electrical engineer to say if the following is dangerous, this worked for me: Snip the 2 wires at the point they connect to your dead motor so you leave a lot of wire still connected to the original pse circuit board. Then for the working donor motor, cut the wires from the donor motor but all the way down by the donor pse unit circuit board so the donor motor still has a lot of wire length connected. Next, strip a half inch of wire off each wire (the 2 connected to the working motor and the 2 connected to the original PSE circuit board) and join the wires together by twisting (black to black, white to white) and then cover the wires with electrical connectors (the small cheap screw-on ones will do). So now without the need to solder, you have a good working motor connected to your original PSE circuit board that is still programmed to do everything you need it to do for your car. Close the original PSE unit with the working motor up carefully and reinstall it in car. Was a $45 total fix for me and has been working fine now for over a year. This should work for any model with contour seats.

 

spigrimace, that's a good plan. I'm still troubleshooting. A scan indicated time out error codes for all of the pse functions, so they were cleared, and we'll see if only the contour seat timeout is reported when scanned again. My pump is noisy enough to be easily heard each time it runs. Is this normal, or perhaps indicative of imminent failure?