I think I am in the correct section now, so I am re-posting my question:

I have a 2009 VDP and the Dash says car too low and it is bottomed out at all 4 corners. I used my iCarsoft i930 reader and got the following Codes:
C2302
C1419
Left front damper status 15

When I start the car, it does not rise at all. I can hear the compressor running, but it does not sound really strong. I have replaced the two rear shocks a year or so ago. Within the last few months, the right rear of the car seemed to sag a bit, after it had been parked for a while, but it would pump right back up when the car was started. My battery is a dealer battery, about a year old. The car has sat for a bit, but it was still starting right up, but I just charged the battery back up.

Not sure where to start, with my diagnosis journey?

 

Looks like you have two problems:
1) You are most likely correct that the pump is getting tired and cannot deliver enough air at a high enough pressure to get the vehicle to rise in the 45 seconds allowed. You should be able to see the pressures live in with your reader to determine the output.
2) The circuit to the CATS solenoid is open on the right hand strut - could be the solenoid/connector or wiring. See PINPOINT TEST G256924p9.

Not sure what the reference to left strut status 15 is all about.

 

I am not familiar with PINPOINT TEST G256924p9, can you explain that for me?

 

Download the x350 workshop manual and do a search for that number. It goes through the tests in detail.

 

OK, found it and just downloaded it.
Thanks

 

I found the test procedure, but I cannot find an EC12 electrical connector pin diagram. Is there a reference for the pin layout, so I can test the specific pins?

 

I use SDD and they are all shown there. Not sure where they are in the manual. The connectors often have pin numbers on them.

 

I was able to do the G256924p9 test on the front two shocks and they seem fine. I checked all 4 shocks and the valve block for leaks, with soapy water and there were no visible leaks at the connections. I drove the car at about 30 mph on the street for a mile or so. I did have all 4 shocks bottomed out. Now the rear two have raised back up and now I just have the two front shocks too low. I cleared the codes after all my messing around and now I just have one Code, the C2302 Leveling Plausibility Error.

 

C2302 usually points to a fault with the ride height sensor or it's wiring.
Have a look at the front sensor for damage, take it off and feel how it moves
look for damaged wiring or bad connector

 

It sounds like the car knows it is too low in the front but cannot get it to go to the commanded height within the 60 seconds allowed. It would have to be reading the height sensor to verify the low condition which you are physically verifying.
As you originally stated, the compressor may not be putting out enough air to get the job done in time. Did you remove the air line and see if air is being directed to the struts up front? Could be a leak that is not detected or a valve not operating.
One would think that with the rears up there should be enough air/pressure to then get the fronts up. You may have to clear the error and do your drive cycle again since it may not try again with the code there. The second run may inflate the fronts but that still would leave the compressor output in doubt.

 

Yesterday I was able to use my iCarsoft i930 reader again and learned how to read the various Data Streams, here is some data I got:


Height Sensors
Front Left Sensor -66 mm
Rear Left Sensor -56 mm
Rear Right Sensor -13 mm

Height Sensor Voltage 1 & 2 5.00 V

Pressure Sensor
w/ compressor on 6+ bar (max)
when compressor off 3 bar
climbs back slowly in between compressor cycles
once compressor is off, pressure drops slowly
pressure sensor supply 5 volts

Damper Solenoid Valves w/compressor off
Front Right Closed
Front Left Closed
Rear Left Closed
Rear Right Closed

Damper Solenoid Valves w/compressor on
Front Left Open
Front Right Open
Rear Left Closed
Rear Right Closed

Damper Status Compressor On Compressor Off
Front Left 0 15
Front Right 0 15
Rear Left 0 15
Rear Right 0 15


Another piece of information, when I turned the car off, and I jumped down by the compressor, I would hear air bleeding off, from the compressor area, for about 30 seconds continuously.

 

I posted a reply earlier however it seems to have disappeared.
Your car seems to know what it is trying to do. It is mainly having trouble getting enough pressure to make it rise to the proper level. When I checked my reservoir pressure earlier today it was at 15.7 Bar. So you can see yours is an underachiever. It will need replacing or rebuilding with a kit.
The air escaping at the compressor may only be the car trying to level itself when turned off. They will do that by letting air release - never running the compressor when turned off.
The system is designed to raise the rear first and then the front. However 6 bar is not enough to counter the weight of the front of the car.
Do the compressor first and see if any other problems crop up after that.

 

I thought I had the air suspension problem pinpointed. I bought two new Arnott front air shocks and installed them yesterday. Last week I took the air compressor out and replaced the piston ring and gasket. When the compressor is on, I can take the air lines off of each front shock and air is coming out of the hose. The two front damper solenoids are open when the compressor is on, then they shut when the compressor goes off. The rear shock seem to be at an acceptable level. When the compressor is on, the pressure gets up to about 6 of 7 bar. When the compressor goes off, the pressure seems to drop and then starts going back up slowly.



The front level sensor (just have one on the front) seems to be working and it reads approx. -71 mm and then slowly raises the car to about -65 mm while it is on. When the compressor goes off, the front level seems to drop back slowly. The rear level does not change.



This does not seem like it should be that hard to diagnose, help!

 

Sounds like your compressor is still marginal. Have you tried releasing the air from the rears to see if they return to normal height? One turn loosening on each rear fitting should let it out. They may go up since the rear is lighter than the front.

 

Bear in mind also that there has been a problem where there was a bad connection
on one of the plugs which connect the "brain" behind the rear seat

 

How can the compressor be marginal, if I replaced the piston ring?

The rear Damper Solenoid Valves remain closed when the compressor runs, so will they open if I let air out of the rears?

I did not understand the latest post.

 

It isn't just the ring that wears, although it should be the part that wears the most. The compressor also has the dryer, which is the chamber full if desiccant beads, and the compressor also houses the vent solenoid, which is theoretically the only way air should escape the system back to atmosphere, when that vent solenoid is opened by the suspension controller.)

Are you still getting the C2302 after replacing the piston ring? C2302 is either a poorly working compressor or an air leak. if you have a leak and haven't found it, throwing money at other parts is just that... throwing money. You mentioned 6 or 7 bar. This is from the dealer training manual for air suspension that's in the How-to sticky thread at the top of the forum page: "The air suspension system does not deplete the reservoir contents below 9 bar (145 Psi) under normal operating conditions."

If you let air out of the rears, the system should indeed try to raise them by opening the solenoids in the valve body. If the fronts are raising but then sagging fairly quickly, then there's nothing for it but you have a leak somewhere.

 

To add to wfooshee excellent post above. When replacing the piston ring on the compressor did you remove the desiccant beads? Were they completely saturated with water?(Yes they ALL are!).
Did you dry out the beads before reassembling the compressor?

I learned from wfooshee that the long term problem with this whole air suspension system is it's inability to remove all the moisture from the air. It was crippled right out of the factory because of this. As time goes on more and more moisture accumulates through out the system. When I took my compressor apart water just poured out.
.
.
.

 

BTW, he has two threads going on this, he started a new one on March 5th, and now both threads are going, same issue.

 

I made the decision to put in a new compressor, since I got a lot of advice that the compressor was probably tired and worn out and leaking, even though I changed the piston ring in my old one already. Nothing improved. My reader says the front dampers are opening when the compressor is on and I have 5.0 volts at each one. The front height sensor starts at -72 and then goes up slowly to -68, while the compressor is on, then drops back to -72 fairly quickly, after the compressor goes off.

If there is a leak, how on earth can you trace it when the hoses are buried inside the floor going back to the trunk.