groves73

I recently bought a cheap key fob and replaced it with the old guts. battery in fob is new. it is having trouble seeing the key sometimes. i put the old key fob back in service and still wont see it. when I push the start button or the lock button on the door handle(when it can see it) the truck pops open?

next issue is the truck wont shut, keeps popping open until you close it 4 or 5 times. when you close it you can hear air swooshing out. I epoxied all the BB ports but I think the big circular piece on the pass side of the switch has breaks in it.

Im not too concerned with the second issue as I assume its a vacuum leak. I dont know why the trunk opens when I push the start button

Any ideas?
2005 sl500

Rudeney

My guess is that the reason the trunk pops open when you press these other buttons is because of the vacuum leak. When you have a leak, the PSE pump will detect this continuous running and eventually shut itself down. This is why it takes 4-5 times to get the trunk to stay closed as you are having to wait until the pump times-out. Now, when you press a button, such the door lock/unlock or engine start, the car will send out a CAN bus wake-up signal, which re-starts the PSE pump and re-energized the trunk lock making it open.

My guess is you have the same leak I did with the diaphragm housing clips being cracked. I fixed mine with some ZIP tires. Check the sticky post about the soft close feature. My post starts a #247:

https://mbworld.org/forums/sl-class-...ix-diy-10.html

As for the key issues, maybe you damaged something when swapping housings? Do you have a spare key and does it behave the same way? If not, you probably should bite the bullet and get one. Yes, they are dealer-only and expensive, but if your one and only key dies or is lost, your car becomes a 4100lb dead weight.

groves73

ok, I zip tied the round part and don't hear the air rush anymore. The trunk is only popping intermittent, Some times it recognizes the key and sometimes it does not. When it does not, that's when the truck pops when pushing the start button. seems to happen when the car is out in the sun. 105 here already. if its in the morning in the garage its does not happen.

If i put the key in the ignition there is no issue? I am also getting key low battery but have replaced it twice with fresh ones

I love the car but these are always something wrong with them!

Is there a way to disable the soft close? pulling a fuse or disconnecting the 2 wire harness on the trunk release?

could it be an alignment issue. the truck release went back in the same spot with the 2 screws.

Where is the best place to get a new key? i know my local dealer will charge too much, is there one online?

Rudeney

I still think this is an air leak that is causing the PSE pump to shut down. This is why the key does not work to open it - there is no air pressure to actuate the lock. But then when you press the start button, the CAN bus "wakes up" the PSE pump and then the trunk opens (as requested earlier when you pulled the handle). There is no way to disable the pneumatic function - it's how the latch works. You still have a leak you need to find.

You can only get keys through the dealer. And with KeylessGo, it's best to let them "program" it. They are supposed to come pre-programmed, but there have been many reports lately keys working out-of-the-box for remote and starting, just not KeylessGo functions.

groves73

these cars have a little satan in all of them, I was not sure if I fixed all the leaks in the trunk opener so i bought a brand new. same fn problem. trunk pops open couple times then gives up it you hold it down. also pops open when you touch the handle or pres unlock on the key pad. they keyless go works sometimes but most times not. I thought I turn the key dependent off but it occasional senses me touch the handle.
never pop open the you put the key in the dash and turn it.
I really hate to give up on this car again. this is my second one. but damn I cant enjoy it!!!!! ac is out and its about to be 100 around the clock here in arizona!$$$$$
any ideas on how to get the trunk to stop popping open? there are some errors about the seats and you can hear air escaping every once in a while, it on the same pse but will that make the trunk pop?

groves73

I tested the line from the pse to the trunk latch. hold pressure. no vacuum leak. truck pops open if i hit unlock on the key remote. something is sending a signal to open the trunk, any ideas suggestions. im going to get a new key, as the old one wont lock the car. I dont think thats the issue since it pops when i press start on keyless or touch door handle.
the extra vacuum storage tank in trunk hold as well.
this has to be an electrical issue.
Rudney any ideas
Thanks

Rudeney

I just have no other ideas! I was sure it was a leak causing the PSE pump to shut down, then later wake-up and pop the trunk. It would have to be a really weird electrical problem, likely with either the KG control module or rear SAM.

groves73

Thanks Rudney. I appreciate your response. I am hoping its a malfunction with the key. once i get a new one I will report back it fixed it. If not I will let you know what cliff I pushed it off so you can pick some parts from it!

groves73

got my new key and i can push the lock and unlock buttons with no trunk popping open! had to test my thoughts on the old key. put the new key in the house, went out with the old key and trunk would pop pop pop, took the battery out of the old key and it closed and stayed shut. got the new key and it opens and close on the first try. Hopefully this will help someone later.
new key does not do keyless go now. dealer first told me it works right from the start. now the parts guy said he didnt know it might need to be programmed and it will be another 180. I will call MB to see what they say. I asked the guy a coupe time before I spent $500 on the key if there will be additional and he said no it will work.
Thanks Rudney for your assistance.

Rudeney

Interesting information! Yes, you are likely going to need to get the key programmed. I a not sure why, because KeylessGo keys used to come working out of the box, but recently, I hear many owners having to get them coded. Now, what will be interested is to see if getting the new key coded if the trunk lock still behaves for it.