2005 BMW 4.8is AIR LEVEL PROBLEMS AGAIN
 

i have a 2005 x5 4.8is, ive been having so many problems with this damn suv, im to the point im tired of messing with it and ready to sell it!. ive had it to 2 shops and 1 BMW dealer and none of them can figure out whats wrong with. first i replaced the air ride supply control module with a used one and had it reflashed, that worked for a day then i took it to the dealer i spent 600 dollars there and they said the module was fine but it needs a right rear sensor, so i had them replace the sensor, so when they went to reprogram it they said that the module wouldnt program and it needs a new module (which is almost 800 dollars) but i got one off ecs tuning for 660. had that programed and now the left front sensor is reading back wards. has anyone ran into that problem? if so please let me know. thanks

I've had meny problems with mine too. i just replaced my two front sensors. the front sensors are the same right to left and i think the tech needs to tell the car what side its on. It took my tech about a half hour or so to set up the everything with the system. what is yours doing exactly? Is it falling down or one corner going down?

right now its pumped all the way up in the front and rear, they are saying that the left front sensor is reading negative voltage and thats causing it to set the light, im just tired of dumping money in this thing. ive spent 1600 on it in the last 2 months and the air ride has been a headache for 4 months!!

so far we have narrowed t down to not being the module since its new and we have swapped the left sensor with right front sensor and it still reads negative voltage, i shoulda stayed with GM then i could scan it since i have a tech 2

Mines been a headache since day one. just spent about the same on mine and I did all the work my self. 2 front sensors 2 front bags and a pump. come to find out after i bought the pump and the old one wasn't bad just making noise because it was loose. where are u located? I never bought a scan tool so i bring mine to avenue imports here in palm beach. they tell me whats wrong and i pay him just for his time he spends with his scan tool. he has a GT1.

My ride height knock on wood stays perfect but my height controller doesnt work, I replaced 2 arnott struts and havent lost air in any of the corners to date, the previous owner replaced the control module.


i think if i replace the compressor my ride height should work, it's probably fried from being overworked when the front struts were leaking.

So here is some help for you guys. Not sure if this will help. All this is from the service history. LF front strut failure and all the shit that the dealer replaced. The dates is the complaint date and the repair date.

01/11/2010 FRONT SPRING STRUT, AIR SUSPENSION (LF) LEAKING
01/18/2010 FRONT SPRING STRUT, AIR SUSPENSION (LF) LEAKING
01/21/2011 AIR SUSPENSION - TRACK ROD LOOSE
04/08/2011 ACCUMULATOR/VALVE UNIT, AIR SUSPENSION (LF) PERMANENT
MALFUNCTION
05/05/2011 AIR SUSPENSION - AIR SUPPLY UNIT PERMANENT MALFUNCTION
05/05/2011 Air supply system for air suspension (LF) permanent malfunction
06/20/2011 AIR SUSPENSION - AIR SUPPLY UNIT PERMANENT MALFUNCTION

So after all of this, and the previous owner paying $50 per visit under CPO, he still paid $350 out of pocket to get it fixed.

All this really tells me, is that the dealer mechs don't know what they are doing either. It seems like they are just replacing shit, and hoping for the best.

With all these issue, and if someone is dropping over $1k into this system, it might be a good idea to switch to coils, and have someone disable the air ride in the computer.

After reading all these posts on the issue, it looks like the following happens.

First, your air spring fails. Car drops. So related components are now air contaminated, which means moisture contaminated. Also your compressor is working overtime to keep it inflated. So, if you neglect the issue, your compressor will fail. I also suspect that your valve unit will fail as well. Think of it like this, if compressor is working a lot, that air, is hot. Aluminum valve unit and fittings start expanding, also leaking. The car also tries to auto level, this I suspect is also done through the valve unit. I am sure it balances the pressure side to side. With leaking shit, I suspect that valve unit working like crazy to keep the car level. Look above, at service. Dealer kept dealing with the left front spring non stop. Accumulator failed, and valve unit failed, I am sure as a result of not addressing the issue promptly.

If your car is jacked up, I suspect the valve unit took a dump, or some sort of electrical relay. Something is not letting it dump excess air.

Why is this system so retarded? I just don't understand why it fails so often and so drastic.

But I have to say, if your car drops one spring, you need to disable the damn compressor right away, not drive the thing, and replace the spring asap. If you keep driving, you are probably going to make other components fail.

rc im in indiana and slickgt1 i havent replaced any of the air struts yet

its letting air out it just wont level since the left is reading negative voltage, im going to run 3 new wires from the sensor to the module and see if that fixes the problem because if it does then theres a break in the wires going to and from the sensor to the module

Seems that the 4 corner air suspension is problematic. I have over 150k miles on my stock '03 4.4 spt pkg X5, even having used the X for thousands of miles fully loaded and towing a 6k lb trailer all air suspension components are original. Was wanting to find an X with the full air system when I was shopping for my X, but now I'm glad I couldn't find one I wanted to own.

Start down a theory of operation discussion road with most techs, mix in some confirmation checks with a meter, add a pinch of common sense, stir well, and you may lose most dealer techs. And the ones that take it upon themselves to really understand are kind of stuck since pressure to produce can preclude the time it takes to follow up on a computer fault indication with actual confirmation. A lot of parts get replaced just because a problem revealed during diagnostic work is incorrectly perceived to also be the cause. No soaks on the folks that do this; the processes in place at most dealers can constrain their efforts. That, and the dealer's hourly rates become spendy quick, so it's rock vs. hard place.

Virtually everything to do with the suspension can be checked by the handy owner except perhaps the computer itself. Compressor operation, wheel sensors, actuating valves, dump valves, etc. Even the compressor head temp is just an analog voltage on a wire under the cargo floor. The question becomes do you want to take it on, and what's your own time worth?

Negative voltage?? ??? In reference to? The sensors have 3 wires, 5v source, return (let's just call it ground for discussion), and the signal. The signal is generally about 2.5v at normal ride height reading in reference to the ground wire. Now like anything else DC, if you read that against the source wire, then it looks negative. Same with your car battery - read it "backwards" and the meter duly reports that the voltage is "negative" with respect to the meter's common. Doesn't mean there is anything wrong with either part. The sensors are just a magnet that rotates inside a field. As the magnet's relative position varies (the arm rotates), there is a minute fluctuation in field current, much too small to be useful. So the sensors have a small microcircuit that scales this effect and provides an output that varies between .5v ~ 4.5v. Since there is no mechanical connection internally (rotating the arm just rotates the magnet), you can twirl the arm completely 360 degrees. If you monitored the output of a working sensor whilst doing that, you would see voltage peaks and valleys as it went around.

The diagnostic software graphically displays the source and signal voltage at each corner, and displays the interpreted relative position (height) as well. From there it is very straightforward to confirm 5v applied to the sensor across source and ground, and to confirm the voltage output of the signal wire - this is a discreet function that can be verified independently of the EHC computer. I'm not trying to bust any chops here at all - I want those in this group who so inclined to, at a minimum, understand enough to be able to inquire of whomever they are paying to do the work, or ideally be able to troubleshoot many of these faults with a modicum of confidence. This isn't magic; it really is just a logical arrangement of inputs, outputs and resulting effects. Ok, maybe you can slam me for using the word "logical" in a thread about the BMW self-leveling system. Let's all take a break whilst I go in the corner and beat myself about the head and shoulders.

Ok, I'm back.

In a post last week I gave the pin outs, wire colors, and functions for all 4 corners of the 2-axle air suspensions. The height sensors can be checked on the car (I'd at least unbolt the bracket with sensor so you can work with it in your hand), or checked on a bench. These stories about folks having techs swap sensors from side to side, or replace something electro-mechanical in the system "because the computer said so" are more than a little bit alarming.

I think what I need to do is a DIY on how to check the function of all the discreet components of the air system. The computer may incorporate speed, cornering forces, if a hatch is open, and so forth into it's processes, but the rest of this system is just a handful of inputs and outputs, or commanded actions re: the compressor, actuating valves, etc. Getting the diag out of the computer is useful, but that is just pointing to the symptom, not necessarily the cause. SlickGT hit it when he suggested there can be causal relationships between failures in one area that can result in symptoms in another. For example, the compressor has a temp sensor on the compressor head. Above a certain temp, the compressor is cut-off for a given period of time. (That temp signal is just a voltage on a wire under the load floor, by the way). Then it logs a code, and an example of a short-sighted part-chucking approach would be to say the compressor is failing.

I'll try to do a complete how-do-I for checking all of the discreet/mechanical parts of the system, but it'll be awhile. Just gotta find some free time.....

Great post Civdiv. Can't wait for your write-up. Let me know if you need some help in gathering anything. Car is in garage, so I can easily go out and check pretty much anything.

Thx slick. I will try but right now working approx 4 a.m. to 6 p.m and most of Saturdays. This will be a challenge to fit in. Right now on my list of things to post into this group:

How to read and verify the inputs and outputs, and verify the operation of the electro-mechanical components of the EHC system.

How to maintain the actual engine coolant temp closer to 200 (vs. 225) if you are so inclined.

How to electronically boost the main line pressure of the transmission under desired conditions (load, throttle, rpm, whatever) if you are so inclined. (you gotta do it "conditionally" or over time the EGS will learn around the firmer shifts and gradually go back to blue-haired granny shifting)

And so on...........

Exactly! Just throw out the air suspension garbage and switch to regular spring or coilovers.

cant wait, i got my snapon multimeter ready to go
my airide light has been on for over a year, no drop in ride height though
im pretty sure my right rear sensor is probly tripping