Self Leveling Suspension Inactive error help needed
 

So I started to get this error a few days ago and had no choice but to drive it home instead of getting it towed. Ride was horrible! Anyways I noticed a few days ago that my drivers rear was sagging down a bit (Single axle air suspension system) so I started the car and it went back up. It’s been holding for a few days now but I’m wondering if it’s because I had a few bags of wood burning pellets which was unevenly distributed in the back seat causing it to sag on that side? I’ve since removed the bags from the back seat. Anyways due to rain I haven’t been able to go out and check leaks on the air bags but if it was leaking wouldn’t it be leaking and sagging daily? Or could it be my pump or sensors? I’m currently trying to track down ISTA software to check if it will give me more details on the error I’m getting but figured it can hurt to post and get some info from all the veterans here.

So needing anyone to confirm if its possible the airbags do have a small leak and maybe my pump has been working constantly without me knowing and if so is there a rebuild kit out there I can purchase? I looked at the recommended ECS Tuning kit but it appears it’s no longer sold. Could it be my sensors?

Thanks in advance

It could also be the accumulator....

Your problem sounds like the pump possibly failed to start but a "reboot" fixed it?

The wood pellets shouldn’t matter. My first guess would definitely be a leaky bag, but they’ve been holding air since the error message? Have you ever replaced them? If a bag is leaking then you will certainly hear the pump running more than usual. Can you let it sit for a couple days and then see if the rear end is sagging? normally the pump doesn’t run very much at all, just over uneven terrain, my sloped driveway approach, etc. Id still lean towards a very slow leak, and a leaky bag won’t fix itself. I’ve used Arnott replacement bags with very good luck (not a fan of their Jeep spring conversion though), and it’s an easy do-it-yourself job.

Beyond that the usual failure points are one of the self leveling switches on the rear subframe, by the air struts, corroded wiring/connector to these switches, or the pump/plumbing itself. There is an eBay guy who sells a rebuild kit to the pump, if it turns out to be that. New ones are expensive.

I just bought this kit for the original pump from my '04 with 4 corner air. The rebuild kit is the same for 2 or 4 corner, but the part is different- be sure to order the correct replacement pump for your suspension.

The rebuild is easy with plenty of pdf's and videos about how to install it. We just got the SLS error again last week in the 4.8. It is apparently the pump. So, my plan *was* to take the existing pump from the 4.8, rebuild it, and then install it into the 4.4- which has started a nice subtle lean to one side. There are no errors yet. We have never replaced the pump on the 4.4 with 60k miles. We used to be able to hear it whirring back there. Since we don't hear it any more, my thought is that the pump will need a rebuild soon enough.

Unfortunately, the wires in my 4.8 pump that I replaced a 5-6 years ago are fried. It appears that the pump got very hot and affected the wires. (See pics). Some of the insulation is off as well as a few hotspots on the wire. Not gonna use it again.

So, my plan is to buy a used Wabco 4 corner pump from eBay- they're everywhere and from ~$150 up. I will then rebuild that one for the 4.4. There are cheap units that are new and not OEM/Wabco, but I don't trust them. This is gonna be an expensive month for BMW ownership. :(

How would I know if its the accumulator? If I had to guess Im just checking to see if air is escaping from the fitting using water and soap right?

Its weird a few weeks back I got the tire low light but when I checked the tires they werent that low. Then the day I got the error same thing happened the tire low light came on and a few minutes later the Inactive Suspension came on. I did notice a few days later when I was driving home for a few minutes the suspension inactive went away and came back and been on since.

The next day I drove home with that error light the drivers rear was sagging lower then the other side. Later that night I went to the car and started it and the pump inflated everything back up and thats when I decided to move the pellet bags around and yesterday it seems to be holding. I havent checked this morning. Since Ive owned the car I have not replaced the air bags and not sure if the previous original owner ever did as well. If it wasnt so cold and raining I would have crawled underneth it to see how bad of a shape they are in.

To me the pump is so faint that I rarely even know its running. Probably doesnt help I like to listen to music while driving either lol. I started the car last night so will let it sit and keep an eye on the rear to see if it starts sagging again. Im currently trying to get ISTA software so I can see more in depth with that. I already ordered a set of Arnott's figured I have them on hand when I do have a chance to go out and check things out.

I found him last night which it seems like alot of people use. Looks like its just seals and nothing more?

Thanks for the link. Ill check it out and may just buy a repair kit and have it on hand while doing everything.

How loud are these pumps supposed to be? Reason I ask is that I can barely hear it. Even when I have the rear lid open and listening I can hear it but its pretty faint. Does that mean its going bad?

Is it common for these pumps to get that hot? I thought these had heat sensors so they turn off if they get to a certain temp? Have you maybe considered soldering on a new set of wires or building a new set from scratch? Color will be off but as long as you color code the wire I dont see that being a problem.

The 4.4 is the only one I could hear out of 3 E53's I have owned with air suspension. Since I could hear it, I sorta assumed it was on the way out. Though that was in 2019, it was less than 25k miles ago. Production dates could be a difference. The 4.4 is a small sunroof unicorn (the 2nd of these I have owned) with an early production date 10/03, IIRC. It could be that early units of the LCI were louder than the newer ones. The 4.8 is a July '04 production.

I dunno ab the heat.:dunno: Some of the used units I saw on eBay also had a little frey in the insulation there so maybe it is more common than we hear. I found a used four corner unit with good wires for $160. If I can get a functional Wabco rebuilt for $200, I am in. :thumbup:

Your question does have me looking for some heat sync fins I could glue on there or use double sided thermo tape. They're all over the place for PC builders. I always figured I would have to add them to my Android radio when it got too hot, but it never has messed up due to heat. OTOH, if this is something that fails every 6-7 years, I may not cross this road again in the 4.8. :shakehead:

How heavy are the pellet bags? They can't be more than three adults, which the X5 rear air suspension should be able to handle with no complaints. My air compressor is noticeable, but it rarely turns on unless it senses an out of level condition. Usually that is when I'm backing slowly out of my driveway, which is level, and the rear begins to do down the approach to the driveway from my street. If I'm going slowly enough it has time to react and try to level the suspension. Then I hit the street and it stops. Beyond that I never hear it. It sounds about as loud as perhaps your HVAC blower in your house? Pretty quiet, but noticeable.

I'm still thinking a slow leak. throw those arnott bags in and see how if the problem is solved.

Use the soap and water test to see if there are any bubbles indicating the bag is leaking. Check the connections from the bag to the pump also.