different air suspension pain 4.8is

[TwinsPoppa]

Originally Posted by pieter4458

Is there a way to recondition the compressor? A new one will cost more than a arm and a leg

Not sure if they can be rebuilt or not but you might have to buy a used one and have it shipped to you - assuming that is something not commonly found there.

[SlickGT1]

I mean you can always rebuild everything. Not sure if it will be cost effective though. I would google that. Like rebuild BMW compressor.

[Bnagy4.8]

Hey Guys, Im having a self leveling suspension inactive fault issue. call me crazy but i feel like my suspension is actually sitting at normal hight for the first time in a long time. normally after i park the car for awhile i come out and notice my front right side sagging super low, and when i unlock or turn on the car it pops back up to the normal ride height. its super weird but since the car has had the fault, like i said it all is normal, no bleeding, or sagging.

could my compressor be fault and be letting air out and finally have gone out?

[TwinTurboGTR]

No, the compressor is just pumping air into the chambers and then going into the bags. If the compressor was at fault, both side would be sagging and not pumping air into either of the bags. There is a leak somewhere in the lines up front. Spray the bags and lines and try to locate the leak.

[pink_roundel]

Originally Posted by pieter4458

I monitored my vehicle since my last post and noticed the following:

1. The height on all 4 corners stays more or less constant over a period of 14 days.
2. The reset of the error code only lasted 7 days before the stupid "air suspension inactive" message appears (again)
3. After the error message appeared the vehicle lifting button inside the vehicle becomes inactive
4. The pump kicks in when the car is unlock, but :

4.1 the sound of it is "hard and coarse" like a Taiwan wheel pump
4.2 The pumps speed gets slower after 20 seconds - like it is pumping against an obstacle until it stops.


Question:
Can the Pressure switch on the accumulator be the culprit telling the pump to fill, but due to the fact that the tank is already filled the pump struggles?

or

Is the Pump just faulty and cannot provide the needed pressure to the accumulator?. (remember the corners does not drop)

But why does the reset of the error code only last 7 days?

I am confused.

Do the accumulators have a one way check valve? Remember that the lines have to be filled before the air pressure starts to lift the heavy beast. That may be why the pump starts to weaken after a few seconds. I have a single axle setup and the whole rear of the vehicle lowers, but I think only one bag is bad. I'll be changing them this week. I'll analyze them and post. They have about 173,000 miles on them.

[dhyrk3]

TwinsPoppa, thanks for this literature!

as I understood, the compressor shouldn't start if the engine is 'off'. And the only possible control to do is to lower the vehicle as long as the ignition is 'on'.

However, what I'm experiencing is, at least every other day, both front sags. As soon as I unlock the door, the air bags inflates to the normal height again.

any thoughts?

Originally Posted by TwinsPoppa

Control Modes (See attached for flow chart)

Sleep mode
If the vehicle is parked, it enters Sleep mode after 16 minutes. No further control operations are executed. A "watch dog" wakes up the control unit for a few minutes every 6 hours (wakeup mode) in order to compensate for possible inclination of the vehicle. (Vehicle height may only be corrected once as air supply unit only operates with engine running.)

Wake-up
In wake-up mode, the control unit is woken up for a set period of time in order to compensate for possible inclination of the vehicle. Inclination of the vehicle can be caused by large temperature differences or by minor leaks. Adjustments to the front and rear axles ensure that the vehicle is visually level. To minimize power consumption, the vehicle is lowered
only. The nominal level of the lowest wheel serves as the nominal level for all other wheels. The lowest nominal level to which the vehicle is lowered is the Access level (-35 mm).

Exception:

if the vehicle is parked at Access level, the vehicle is lowered to max. -50 mm in wake-up mode. If the vehicle is parked for a prolonged period of time and there is a leak in the system, further loss of pressure does not produce a change of ride level since the weight of the body is born by the auxiliary suspension and the residual tire pressure.

Advance /Overrun

When the vehicle is woken out of sleep mode by the load-cutout signal (VA), it normally enters advance / overrun mode. Since the engine is not (no longer) running in this mode, however, there are restrictions on the control operations that can be performed in order to conserve the battery. Ride level compensation is restricted to tolerance ranges of 20 mm and 25 mm in the up and down directions respectively. This serves to reduce the frequency of control operations. All control operations in advance / overrun mode are executed as long as pressure is available in the accumulator. When the accumulator is empty and the engine is turned off, control operations are directly driven by the compressor. User-activated changes of ride level and filling of the accumulator are not possible.

So, after 15 mins, X goes into Sleep mode. After 6 hours its supposed to go into Wakeup mode and compensate as long as there's enough pressure in the Pressure Accumulator. Have you observed what it looks like overnight (after 6 hours)?

If your X tries to correct the ride height after 6 hours, but does NOT, then maybe there's not enough pressure in the Accumulator because either its faulty or the compressor in the Air Supply unit is bad (could not pump enough pressure into the accumulator before going into Sleep mode). I assume that the EHC2 module (Control Unit) is working properly as this is what gives the commands and the rest of the system executes them.

This still does not point to where the problem is exactly. This is also assuming there's absolutley no leak (which is still my best guess). I know, lots of assumptions.

Okay, so someone correct my thinking or feel free to comment.

[SlickGT1]

Originally Posted by dhyrk3

TwinsPoppa, thanks for this literature!

as I understood, the compressor shouldn't start if the engine is 'off'. And the only possible control to do is to lower the vehicle as long as the ignition is 'on'.

However, what I'm experiencing is, at least every other day, both front sags. As soon as I unlock the door, the air bags inflates to the normal height again.

any thoughts?

At least one of your fronts is leaking.

[Bnagy4.8]

Please tell me if there is an answer for my strange predicament..

I noticed about 2 months ago that my truck would wake up in the mornings and pop up. I also noticed that one side was sagging in the morning (front right) but it never set off any fault.
So about a little over a month ago my 2005 4.8is displayed this self level suspension inactive fault. However my led on the dash was still lit but non-functional. I took it to the dealership and they said they found no problems so they erased the code. once again all was functioning. lasted about a week with no sagging or popping up in wake up mode. then the inactive fault appeared again. this time the LED was out. once again took it in and they said they found a microscopic leak and said both struts needed to be replaced $1500.

(I was a little skeptical given what happened next).

so I told them to basically F off. Took my truck home, no issues. parked it again, later inactive fault was back. But the LED was still present but un-functional. It has been like this ever since now going on 2 months. The truck hasn't sagged, hasn't popped up/ woke up. ride is a little bumpy but not noticeable. handles fine. nothing the complain about other than the stupid inactive notice.

sucks that I cant use the ride height adjuster but not a huge deal. I'm just super confused as to why my truck is throwing a fault. if it was a leak then I would be sagging like crazy by now.

any ideas.


FYI, I did here somewhere that installing LED angel eyes can cause the inactive fault to be present. and all this started about a week after I upgraded to LED bulbs.

why would this matter?

[SlickGT1]

Power sedative cars.

You most likely have a leak in your bags. Why it doesn't leak all the time, because of the way the bag rolls it's lip and edge. You got the SLS error because you are essentially burning out you compressor constantly filling up the bags. You really should replace them soon. There some nice DIYs here, including a video one. Arnott bags cost under 400 each and carry a lifetime warranty.

[sockethead]

There are so many things that can cause the error on the dash. If you can post the specific error that the dealer found, we can help you better.