1772 Code and Chassis System Fault
Thread Starter
2nd Gear
Joined: May 2026
Posts: 2
Likes: 0
1772 Code and Chassis System Fault
I know I know, there so many good write ups, I have been reading a ton. I just don't understand my how it could be any of those. I don't hear any air leaking from any of the struts, the car sits perfectly level and doesn't drop after time. The code goes away at when I turn the car off. When I turn the car back on, without fail, the compressor will run for a little under a minute and then shut off, which is exactly when the CHASSIS SYSTEM FAULTY warning comes back. The car takes remarkably long to air up, but normal air down time.
I am clearly leaking air right? Why else would the compressor feel the need to run on every start up. But how am I leaking air if the struts never lose air with time? And there is no audible air leaking?
I am inclined to buy a compressor rebuild, but that wouldn't fix the suspected issue of leaking air, it would only help a weak compressor. Maybe it is a weak compressor which would mean I am not actually leaking air, but instead I am never getting to proper pressure, and the compressor gives up and throws the code.
I have also read that the next plausible cause of the issue is the air strut pressure valve. If this were bad, wouldn't I notice sag on a corner of the car? Or at least be losing height with time?
Any widsom is helpful, thanks for taking the time to read
EDIT IMPORTANT (?): I also just moved the car from Arizona (low elevation) to Colorado (much higher elevation). In Arizona, I would get this chassis system fault very intermittently, and the raise times would be normal. Ever since being in Colorado, the fault has been regular and repeatable, and the raise times are much longer. Not sure if the elevation plays a role, or might help with diagnosis
I am clearly leaking air right? Why else would the compressor feel the need to run on every start up. But how am I leaking air if the struts never lose air with time? And there is no audible air leaking?
I am inclined to buy a compressor rebuild, but that wouldn't fix the suspected issue of leaking air, it would only help a weak compressor. Maybe it is a weak compressor which would mean I am not actually leaking air, but instead I am never getting to proper pressure, and the compressor gives up and throws the code.
I have also read that the next plausible cause of the issue is the air strut pressure valve. If this were bad, wouldn't I notice sag on a corner of the car? Or at least be losing height with time?
Any widsom is helpful, thanks for taking the time to read
EDIT IMPORTANT (?): I also just moved the car from Arizona (low elevation) to Colorado (much higher elevation). In Arizona, I would get this chassis system fault very intermittently, and the raise times would be normal. Ever since being in Colorado, the fault has been regular and repeatable, and the raise times are much longer. Not sure if the elevation plays a role, or might help with diagnosis
Last edited by griffinregan; May 18, 2026 at 10:38 PM.
Rennlist Member
Joined: Aug 2003
Posts: 650
Likes: 32
From: Philadelphia
I get the various setups confused but these systems do use check valves. It's been a long time since I had a 955 with an air problem and my current one acquired last year is trouble free (knock wood)
Saying all of the above. Back when these were new I did have an issue with one corner and it did not transfer over to the other corners. So I know that there must be check valves to protect each corner -- or it's part of the valve/ controller. BUT -- There still could be a leak between the pump and the reserve tank requiring a charge each time.
I have never checked -- does the system do a "run check" of the compressor every start ?
Mercedes has the pump come on for a short run every key cycle -- they must assume it's best to make sure the pressures are perfect. The main controller times the pump run -- if it's too long you get the warning. Too long could be the pump being weak or the system is not just a tiny bit low of pressure.
Saying all of the above. Back when these were new I did have an issue with one corner and it did not transfer over to the other corners. So I know that there must be check valves to protect each corner -- or it's part of the valve/ controller. BUT -- There still could be a leak between the pump and the reserve tank requiring a charge each time.
I have never checked -- does the system do a "run check" of the compressor every start ?
Mercedes has the pump come on for a short run every key cycle -- they must assume it's best to make sure the pressures are perfect. The main controller times the pump run -- if it's too long you get the warning. Too long could be the pump being weak or the system is not just a tiny bit low of pressure.
Thread Starter
2nd Gear
Joined: May 2026
Posts: 2
Likes: 0
UPDATE: Water ingress
So I haven’t seen the chassis system fault in 2 days. However I have seen a bulb indicator fault (they all work fine) and a bunch of white noise coming from my speakers. Felt a few drops of water on my feet, knew I had to check my drains
Behold, AC evap drain had TONS of water in it. Would this being clogged cause water to drip in the driver footwell above the gas pedal? And would a wet DRIVER footwell cause all these problems? My passenger footwell is pretty dry (apart from all the water I just dumped on it from the ac evap drain)
I can’t see much on 955/957 having a wet driver footwell, seems that passenger is far more common. Would symptoms still be the same?
Behold, AC evap drain had TONS of water in it. Would this being clogged cause water to drip in the driver footwell above the gas pedal? And would a wet DRIVER footwell cause all these problems? My passenger footwell is pretty dry (apart from all the water I just dumped on it from the ac evap drain)
I can’t see much on 955/957 having a wet driver footwell, seems that passenger is far more common. Would symptoms still be the same?
Intermediate
Joined: Jun 2021
Posts: 25
Likes: 6
From: Norway
I gave up on my own 2007 CTT, after having spent close to $2000 on parts for the air suspension. However, I recommend you do the following if you want peace of mind: Replace all residual pressure holding valves and cut the airlines back a couple of mm's, swap in a new air compressor or rebuild the one you have, replace the valve block, replace the relay for the compressor, peel back the carpet on both sides and check and repair the splices if corroded, open the level control module and make sure there are no bad solder joints. This will help you rule out many common problems. If you still have a problem then may God be with you... Shock replacement next, which is not cheap.
