2013 GL 450 with 27000 miles.
Received a malfunction message and the car ride was extremely rough over speedbumps and potholes. Saw compressor cooling message as well. I press the raise ride height button and it would just blink continously. Stopped the car and you could hear hissing from drivers side rear wheel. I bought an A-2596 Arnott replacement bag and it looked measurably shorter than the OEM bag I removed. Like a few inches shorter. Putting the new bag in was okay but it sure seemed that it wasn't long enough. It did not fit in tight seemed like it was almost too short. I compressed the spring a little to get it in there. Lowered car for test drive. Malfunction message appears. Drivers side rear wheel still looks like it is lowered. Front looks okay. Now when I press the ride height button it will flash and than remain solid but I don't think the car height changed at all. When I press it down I see the message lowering and it will keep doing that until i turn off the car. I don't receive any OBD II codes now. On my bluedriver OBDII reader I am showing old codes :

C156F - The signal values of the level sensors are implausible
C1572 - The correction time when filling is too long

I bumped the cap off of the level sensor with the bag when putting it in and then snapped the cap back on.
I did not remove the 40 amp fuse when working on the system. I can't get the thing out. I've bent the tab and tried to pull it with pliers and I don't want to damage it. I have another 40 amp maxifuse that looks a little different that the clear fuse. Those clear fuses are weak I pull back the tab and try to pull it with pliers and I can't get it out and have to stop applying pressure so I don't break it to pieces. Maybe I'll disconnect he battery and rip it out with pliers. It should come out with just one tab correct?

Going forward: I ordered another a-2596 for the other side (It really looks shorter and not the same size) This is the correct part right?
I ordered an iCarsoft MBII

Is my next step take off the fender to access the compressor and make sure it turns on when I start the car? It's hard to tell if the compressor is even running. (I never paid attention to it before, it just seemed to work)

My concerns:
I may have a bad level sensor but I don't know which one yet.
The compressor might not be running but the airbags might now be full since I repaced the leaking one.
I'm sure if the A-2596 is the correct part because it looks alot shorter than the part I pulled out.
When I press the button to lower the vehicle lowering shows up on the display but nothing gets lowered.

Any advise would be appreciated. What everyone says is an easy fix it now my nightmare.

 

First of all you cannot rely on a generic OBD2 device to diagnose your MB. This is totally wrong. Find someone who has a STAR/Xentry system or buy a cloned system from a Chinese vendor and then read the real trouble codes from each module. The iCarsoft MBII is OK to use but I got the cloned Xentry. The iCarsoft is $150 and the cloned Xentry is about $500-600. The extra cost will buy you some peace of mind if you are planning to keep the car for some time.

From the info you provided you might have a defective level sensor but it can also be out of calibration. With the Star/Xentry at least it can tell you which sensor is the problem then you can further diagnose. The shorter A-2596 might be caused by the air pressure. Once installed the computer will automatically adjust ride height based on the level sensor feedback. One thing you might need to do is to calibrate the level sensor. I'm not sure if the iCarsoft can do it but my cloned Xentry can do it, with the help of an inclinometer (or a smartphone app with your phone). If it takes long to fill the air spring, then you ave a leaking line or defective compressor.

A2596 is the correct part for the air spring but it doesn't help with the rough ride. The problem with rough ride should reside in the strut/shock absorber. The air sping is just an air spring. For the compressor, you might want to do some preventative maintenance to the compressor by replacing the air filter and the dessicator, as well cleaning out the brush dust in the motor and inspect the brushes. There's also a kit to rebuild the compressor replacing the pistong ring and some rubber o rings.

 

I have the ICarsoft for my 2013 GL and it is useless for Airmatic diagnostics. Doesn’t tell you anything. Sounds like you have a compressor that is bad. I replaced mine with an Arnott compressor Very easy with just basic tools.

 

MBII sucks. The compressor works because the front raised when I pressed the button to raise the vehicle. I was looking at the MaxiDAS 808 but would a cloned system be better? They are both about $800 but worth it to me if I will open my eyes to see the voltage to the level sensors and have the ability to raise/lower each corner and calibrate. I have a passthru cable and a MS SurfacePro that I thought about trying out.

 

I have the cloned system and it's amazing. I got it from aliexpress for less than $500 but it doesn't include laptop, just the hard drive. I got the solid drive but if you opt for the mechanical drive it will be cheaper. I have an old thinkpad T41 laptop I throw the drive into it but it required an activation the seller helped me with it using teamviewer. You need some computer knowledge to do this otherwise just buy the system with laptop, which is about $600 or so. The activation only works for a year but we can easily get away with it by modifying the system time of the laptop. Just don't connect to the internet. It has almost all diagnostic functions of Xentry just cannot do SCN coding or software update. It might be able to do software update if you can get the software somewhere, but I don't have the gut to deal with it.

 

I was able to get Xentry passthru working with a Toyota MVCI J2534 cable

I can actuate every corner. When I try to calibrate the left rear reading won't change from 123-124 when all corners should be 26-36. Trying to calibrate all the corners move around until the compressor gets hot and I shut it down. I guess I will take a wheel off. The left rear corner does raise and lower while the reading stays the same at 123-124. This makes me think that the level sensor is bad/broken. It appears there is power at the sensor. So a bad level sensor can make the whole car droop in the back and display malfunction and cause all the other corners to go crazy trying ot compensate I guess?.

 

You can detach the sensor and move the sensor by hand see if the reading changes. If it doesn't then the sensor is bad.

 

I moved the sensor and it changed when moved. After closer inspection I realized that I had the army on the sensor pointing the wrong direction so it was permanently at 123-124 mm above zero. I installed it correctly now and the left corner appears to be consistently 72-92 mm below zero. The right front corner is about 4 mm above. The left front and right rear are about 30-40 below zero. I need to bring the right front down or the left rear up. When I try to do the calibration it fails when the left rear pressure reaches about 21 bar. The calibration always seems to fail at the left rear. Voltage is always lower at that sensor. which makes sense since it actually lower.

 

I may have a fount the problem. The long arm that connects to the sensor on my vehicle is not straight. It is bent. I think that might give the reading of +4 on the right front which may explain the reading of -72 on my left rear. Make sense?

The long arm connected to the sensor on my vehicle is not that straight.
n idea.

 

Well that's a good indication of defectiveness if the arms are different between left and right.

 

This plastic arm is curved, at least it is on mine, on both sides

 

Okay I finally have a decent tester and I receive an error. The left "rear level control valve" failed actuation test.

The valve is bad or there is a leak in the line. I was trying to calibrate the airmatic system and I could not get the vehicle within spec to perform calibration. I could raise the left rear corner within -40 for spec but all the others were then too high. If the other 3 corners are in range this corner is too low.

I can raise the left I did have it up in the error. I think I might replace the valve block and see if I can calibrate the vehicle.

 

So what was that, finally? The valve block, strut, or something else?

 

It was the valve block.