W220 PSE Issue with a twist
 

Hi all, first time post :) I have a 2004 W220 S 500 LWB UK model with a PSE issue. I googled around and searched this forum, but I couldn't find an exact match for the problem I have, but there were a fair few similar posts. OK, so I'd been aware that I had an air leak from my boot actuator for some time, but it didn't bother me enough to do too much about it. I'd already tried and failed to source a replacement second hand part, paid £80 in labour only to find out it was wrong and didn't fit. I'd simply become used to just slamming the boot lid a bit harder, the assist handle retracted and since all the other doors soft close was working OK, it didn't seem worth spending the additional cash.

Anyway, today the car went in to a local independent for an A Service. I reminded the counter staff on the way out that the service book was in the boot (trunk) so they could stamp it. When I came to collect the car some hours later, I found it was unlocked, the boot assist handle was still protruding and I couldn't operate the central locking from the key. It occurred to me that whoever retrieved the service book didn't shut the lid of the trunk properly and the PSE pump probably shut down as a precaution because of the leak. I thought I could simply reset using the trick of pulling the fuse or disconnecting the battery for a while, but neither of these cured the problem. I thought the PSE pump is probably fried, but I can still hear a whirring noise from it. The 20 amp fuse under the rear seat is good, I can press the unlock and lock buttons on the key or in the cabin and get a good 10-15 seconds of whirring from the PSE unit, but I can't get the doors to central lock or soft close. When I push the door lock buttons down manually there is some resistance as though the vacuum is still active.

I suppose my main question is despite the whirring from the PSE, is it fried and do I need a new one or can I try and reset it some other way? I can source a second hand PSE for about £250, but I don't want to waste my money if that isn't the problem. Is there a sure way to determine that the PSE is dead, even though it still appears to be trying to do something when I press the lock/unlock buttons?

Finally, does anyone know the correct part number for a W220 2004 S500 LWB UK boot actuator as this seems to be the original source of the problem.

Grateful for any help and apologies as I know there have been a few similar threads.

Spudnik

For the correct part----post your VIN

Any thoughts on how to determine if the the PSE is completely broken without buying a new one to test?

Yea, put the PSE back and find a friend with factory diagnostics who in five minutes can interrogate the central locking system for faults(find the problem) or continue with your FUYA approach and find nothing!

FUYA...? Kind of hostile aren't you? I was only asking. Not all of us have friends with diagnostic kits and bags of know how. Some of us are simply stuck with the dealer or local independents. I haven't taken the PSE out, in fact I haven't touched anything yet, I was simply seeking some advice before taking next steps and trying to ascertain part numbers. I also posted the VIN as you requested.

OK, so couldn't find a friend with a diagnostic kit, but found a dealer who read off the codes for me. They cleared a bunch of PSE faults, but the one that kept coming back was:

The sensor cable or sensor supply of component B24/16 (Trunk lid opening angle detection sensor) has short circuit to ground or to battery voltage.

For anyone else following this thread, it seems that that the PSE is still operating the central lock on the fuel filler flap. It will lock the flap, but not unlock it. I can manually retract the lock from the trunk and then lock it again with the remote key.

My understanding of the PSE pump is that, it goes both ways. Pumps and sucks.

....creates pressure by pumping and also creates suction as a vacuum. One way Locks, One way Unlocks

So, it could be your PSE pump still..... only working one way instead of both.

I could be wrong, I certainly don't know everything. (like what FUYA means)

You may have to buy a PSE pump if you don't have a friend local with a W220.who will let you borrow theirs for a few minutes to test your car's PSE operations.

Shipping costs may prevent it from being a good deal for you buying from the USA, but I have 2 PSE pumps that I'm not using that I'm willing to sell. Send me a private message if you're interested and we can chat more,

Good Luck.

Thanks Shoeman

I've ordered a new trunk actuator to address the leak. There are breakers yards locally that have the PSE unit for a little less than half the price of a new one, plus they give 3 months warranty, so that's good. I think by the time you add shipping costs and customs charges, getting one from the US will be cost prohibitive. Thanks for the offer though and I'll report back next week when we've tried the new actuator out.