2008 e550 @93K miles

Hello, I am posting to see if anyone reading this has run into this issue and hopefully can offer some guidance on what to do. For some background context, before today's work, the car's air suspension system was working fine (aside from the rear passenger side bag leaking). No codes, no warning lights. I replaced the front struts with Arnott struts around 3 years ago and they have maybe 15k on them (the 550 is not driven much), all trouble free miles. The install of the front struts were completed without issue and I replaced the compressor at the same time, again no issue, everything working.

About 2 weeks ago, I noticed the rear passenger side sagging and knew it was time to replace. Today, I replaced my the rear air bags using Arnott 2724s and replaced both sides. The project was very straightforward and I was able to physically complete the task without any issue. I had the car on a lift while I was working. I used this FCP Euro DIY video as my guide:

Once I reinstalled the rear tires, I lowered the lift so the tires touched the ground and stopped. My intent was to crank the car and allow the compressor to fill the rears before letting the lift go all the way down.

Once I cranked the car, the suspension malfunction warning came on and the compressor did not cut on nor were the self levelers doing anything to level the car. The front struts were pretty high (see pic) which I assume is from being on the lift. I assume nothing is working due to the malfunction code shutting everything down.



I tired disconnecting the battery to see if it would jog the system and I went back and double checked the wiring harnesses connected to the rear bags. This did not work. I started to sense that I needed a way to manually cycle the compressor but realized I likely needed a scan tool to do this (which I do not have at the moment).

So, I called a mobile mechanic and he said he could come scan and tell me what was wrong. His scanner did not look like anything special so I did not suspect it was anything that was going to allow me to see what was going on the in the suspension module. He told me there were codes present but that car was "locked out" due to me not disconnecting the battery before swapping the bags. With it being locked out, he could not see what was going on. He told me I was going to have to take it to the MB dealer and they could reset the system as any 3rd party tech with 3rd party tools cannot unlock it. I am a little skeptical of this as I sensed he really didn't have the right scanner. I am also skeptical of the battery comment given I did not unhook the battery to do the front side a few years back. But it could be true, I really don't know. Plus the DIY video mentioned nothing of needing the battery to be disconnected.

Sorry for being so long, I just wanted anyone reading to know the background. What I suspect is the issue is that the front struts are too high causing the ride height sensors to freak out and throwing the malfunction code. This issue is not allowing the system to run and correct itself. Right now the car is still sitting on the lift until I figure out what to do next.

Here's my current options as I see them, I would love some feedback from others who may have been in this situation:

1.) I gain some knowledge here on a type of scanner I can buy that will allow me to clear the codes and cycle the compressor. I am a competent home mechanic that has used scan tools to diagnose sub module issues on other German cars (BMW) in the past. If I had the right tool, I feel I would troubleshoot it myself.

2.) Trailer it to a trusted local Indy who will charge me a $125 diagnostic fee to use his scanning tools and try to reset the system. He said he cannot guarantee he can fix if it really is locked out.

3.) Trailer it to the MB dealer and get raked over the coals to get the system reset.

If the module truly is locked, would it be best just to take it straight to be MB dealer? I am a little skeptical this is the situation but I could be wrong and would like to know that upfront.

Thanks to anyone that has taken the time to read this. I greatly appreciate it.

 

After doing some more research, I read you can apply 5v to the front struts to let air out. My hunch is that if I let a little out of the front to get it back in a normal ride height range the system will kick itself on.

I’ve also read that it looks like I’m going to need STAR or an equivalent programmer to get this right.

As of today I am going to try the 5v to let some air out, disconnect battery and see if it works. If not it seems I need to find an Indy with STAR or I’ll wind up at the MB dealer.

I’m hoping some folks here can weigh in. Thanks.

 

I think I’m having the same issue as you on my gls450. I replaced the rear airbags after they were sagging. When I lowered the car, the back wheels don’t come up as much as the front ones do. I had to move the ride height sensor attachment to get my air bags out and didnt re position them exactly before lowering g the car. I’m thinking that the ride height sensor got moved which is causing the rear of my car to not rise as much as the front. Not sure if we just have to adjust the ride height sensor or have to get the ride height sensor calibrated after it is moved?

 

I ended up buying a Youcanic programmer to try and diagnose whatever codes are present in the suspension module. It will likely be another week before I can get try it out. My 550 ended up leveling on the fronts when lowered the lift enough to make the self levels wake up maybe?

My hope is since that idea ended up not waking the system up is that once I clear the codes, the compressor will cut on and all will be well. I justified buying the programmer since it’s likely what I would have paid the MB dealer and it works on other cars too.

I report back to this thread once I take another shot at it in about a week.

 

Any Luck? I am having a similar issue.

 

Yes, you just reminded me to post the outcome. The Youcanic scanner worked great and all I had to do was clear the stored codes and it all came back to life. I highly recommend it as I can use it on nearly any car 1996 and above. Good luck.