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Air Suspension Raising Above Low Level I Not Possible
Another PASM diagnosis thread!
Some background: I have a 2011 Cayenne Turbo, with ~88,000 miles. Though I don't think it impacts the air suspension, I'll note that it does have PDCC. I purchased the vehicle in February 2022. The car appears to have been a dealer trade-in. The service records indicated the technicians recommended auction due to transfer case issues, and leaking in the air suspension. I had an independent Porsche specialist (recommended by a different Porsche dealership) inspect the car and he didn't think there were leaks in the air suspension, though he didn't keep the car overnight. I planned on a full suspension refresh at about 100,000 anyways even if there were no leaks, so the probability of there being a sneaky leak wasn't a deal-breaker.
From last February to last December I didn't have any suspension issues from a functionality standpoint. I detected the compressor running often (every drive, at least), but it didn't sound like it was running for extended periods. I frequently cycled the suspension up and down.
Late in December 2022, we had a cold spell--several days of single digits. During that cold spell, the car threw a warning and said that it wasn't possible to raise the suspension and it shouldn't be driven. PASM indicator lights said it was at the loading height. So I didn't drive it. My first instinct was that some valve in the compressor or valve block was stuck, since it was so cold and there's almost certainly moisture in the system (since the compressor has been running). A few days later, when it was warmer, I went back out and tried to raise the suspension, and it went up and down without issue. This seemed to support the valve-sticking hypothesis. But I didn't drive it because I was suspicious and didn't need to go anywhere. A few days later I tried to raise and lower the suspension again, and the suspension wouldn't go up past low level 1. That's how it's been ever since. It'll go between the loading level and low level 1, but not to the normal height. Any attempt to tell the suspension to go to the normal height or above results in a warning that it's "not possible." Since it's gotten much warmer , the valve-sticking hypothesis seems implausible.
Though hearing the compressor running suggested a new fuse and relay wouldn't make a difference, I installed new ones anyways. I could tell that the old fuse was not blown. (I watched this video for assistance:
. Note that the relay in my car was behind the driver's kick panel, but was not in the exact same location as in that video, and it was not as easily accessible as in that video.)
I picked up a PIWIS 3 system. Since I'm still learning the system, I put it in V mode, and started poking around in the faults and real-time data.
Initial readings, after letting the car sit for several days, without being in jack mode.
Sorry for the terrible pictures. I think the relevant faults are 000284 and C1208A. There are some electrical faults that I think were associated with low battery voltage. (I've since picked up a power supply to use when running PIWIS.) Also note that the "level control" indicated it was in "limp-home" mode, and there was 77 liters of air in the system. Also note that the front right and left air bags had nearly the same pressure in them (8.07 and 8.09 bar, or ~117psi), whereas the rear left was 8.42 (122psi) and the rear right was 7.17 (104psi). The system pressure said 2.2 (32psi). The height deviation from required level was -20mm (front left), -26mm (front right), -17 (rear left), -19mm (rear right).
Second readings, after turning the car on and removing jack mode.
Turning the car on allowed the compressor to run. I put the car into low level 1 (the highest it's willing to go). It doesn't say limp-home mode anymore. Height reads are: 2mm (front left), -4mm (front right), 1mm (rear left), -1mm (rear right). I also cleared the codes while I was at it. I didn't check the total system volume or pressure.
Third readings, after letting the car sit overnight in jack mode.
The next morning, having let the car sit with the suspension in jack mode, the readings are -6mm (front left), -5mm (front right), -18mm (rear left), -8mm (rear right). I didn't check the total system volume or pressure.
Fourth readings, after letting the car continue to sit for another day still in jack mode.
I think "Adjustment not possible" and "Availability restriction" are due to being in jack mode. The height deviations now read: -6mm (front left), -2mm (front right), -27mm (rear left), and -11mm (rear right). System pressure: 3.2bar (46psi). System air quantity: 81 liters.
Fifth readings, after turning the engine on and turning off jack mode.
Immediately after the fourth readings, I turning the engine on, removed jack mode, and let it run for a few minutes. The 000284 and C1208A codes had not reappeared, though I hadn't driven the car at all. The car still indicated that normal height was not possible. The height deviations were: -2mm (front left), -3mm (front right), -1mm (rear left), 6mm (rear right). System pressure: 4.6bar (67psi). System air quantity: 94 liters. Strut pressure: front left was 7.94bar (115psi), front right was 7.95 bar (115psi), rear left was 7.65bar (111psi), rear right was 6.92bar (100psi).
Tentative Conclusions
I have spent quite some time reviewing the threads on Rennlist and elsewhere, but admit I have trouble synthesizing the information. My tentative conclusions are:
The compressor is ok. It's definitely capable of operation, since I hear it running.
Theory: While (as I've read elsewhere) the ordinary quantity of air in the system is about 120-130 liters, and this compressor won't seem to get to that point, maybe it's because there is too much leaking from the rear air springs.
But maybe it's just not actually compressing the anymore for some reason, or maybe there's a valve stuck in it, which is preventing the air from actually getting where it needs to go. Thoughts?
The rear left air spring has a serious leak, and the right rear air spring has a smaller leak.
So even if the problem preventing the suspension from raising problem is from the compressor or valve block, these are going to need to be replaced soon anyways.
Maybe the front air springs are leaking, maybe not.
When in jack mode, the front air springs appear to lose a small amount of height--at least that's what the PIWIS is indicating. Does anyone know what the margin of error is on the PIWIS calculated height expectations?
It looks like I'm going to need to replace at least the rear springs, and if I do that, I intend to fill with nitrogen. But if I do that, and there's still a small leak from the fronts, it won't take too long before the compressor is putting atmospheric air into the system again anyways... right?
Maybe there's a problem with the valve block.
Since this part isn't too expensive to replace, maybe I should just go ahead and do it when I replace the struts.
I haven't put the car up on a lift yet to specifically inspect the air springs, largely because I'm hesitant to drive it right now. Any suggestions for further diagnosis?
This is what I worry about with my 2011 S as I'm coming up on 120k miles. Anyone get this done lately as I'm wondering what would be a ballpark estimate to have an indy replace all 4 air shocks (parts & labor)?
Some background: I have a 2011 Cayenne Turbo, with ~88,000 miles. Though I don't think it impacts the air suspension, I'll note that it does have PDCC. I purchased the vehicle in February 2022. The car appears to have been a dealer trade-in. The service records indicated the technicians recommended auction due to transfer case issues, and leaking in the air suspension. I had an independent Porsche specialist (recommended by a different Porsche dealership) inspect the car and he didn't think there were leaks in the air suspension, though he didn't keep the car overnight. I planned on a full suspension refresh at about 100,000 anyways even if there were no leaks, so the probability of there being a sneaky leak wasn't a deal-breaker.
From last February to last December I didn't have any suspension issues from a functionality standpoint. I detected the compressor running often (every drive, at least), but it didn't sound like it was running for extended periods. I frequently cycled the suspension up and down.
Late in December 2022, we had a cold spell--several days of single digits. During that cold spell, the car threw a warning and said that it wasn't possible to raise the suspension and it shouldn't be driven. PASM indicator lights said it was at the loading height. So I didn't drive it. My first instinct was that some valve in the compressor or valve block was stuck, since it was so cold and there's almost certainly moisture in the system (since the compressor has been running). A few days later, when it was warmer, I went back out and tried to raise the suspension, and it went up and down without issue. This seemed to support the valve-sticking hypothesis. But I didn't drive it because I was suspicious and didn't need to go anywhere. A few days later I tried to raise and lower the suspension again, and the suspension wouldn't go up past low level 1. That's how it's been ever since. It'll go between the loading level and low level 1, but not to the normal height. Any attempt to tell the suspension to go to the normal height or above results in a warning that it's "not possible." Since it's gotten much warmer , the valve-sticking hypothesis seems implausible.
Though hearing the compressor running suggested a new fuse and relay wouldn't make a difference, I installed new ones anyways. I could tell that the old fuse was not blown. (I watched this video for assistance: https://youtu.be/gZ-eCPixFX8. Note that the relay in my car was behind the driver's kick panel, but was not in the exact same location as in that video, and it was not as easily accessible as in that video.)
I picked up a PIWIS 3 system. Since I'm still learning the system, I put it in V mode, and started poking around in the faults and real-time data.
Initial readings, after letting the car sit for several days, without being in jack mode.
Sorry for the terrible pictures. I think the relevant faults are 000284 and C1208A. There are some electrical faults that I think were associated with low battery voltage. (I've since picked up a power supply to use when running PIWIS.) Also note that the "level control" indicated it was in "limp-home" mode, and there was 77 liters of air in the system. Also note that the front right and left air bags had nearly the same pressure in them (8.07 and 8.09 bar, or ~117psi), whereas the rear left was 8.42 (122psi) and the rear right was 7.17 (104psi). The system pressure said 2.2 (32psi). The height deviation from required level was -20mm (front left), -26mm (front right), -17 (rear left), -19mm (rear right).
Second readings, after turning the car on and removing jack mode.
Turning the car on allowed the compressor to run. I put the car into low level 1 (the highest it's willing to go). It doesn't say limp-home mode anymore. Height reads are: 2mm (front left), -4mm (front right), 1mm (rear left), -1mm (rear right). I also cleared the codes while I was at it. I didn't check the total system volume or pressure.
Third readings, after letting the car sit overnight in jack mode.
The next morning, having let the car sit with the suspension in jack mode, the readings are -6mm (front left), -5mm (front right), -18mm (rear left), -8mm (rear right). I didn't check the total system volume or pressure.
Fourth readings, after letting the car continue to sit for another day still in jack mode.
I think "Adjustment not possible" and "Availability restriction" are due to being in jack mode. The height deviations now read: -6mm (front left), -2mm (front right), -27mm (rear left), and -11mm (rear right). System pressure: 3.2bar (46psi). System air quantity: 81 liters.
Fifth readings, after turning the engine on and turning off jack mode.
Immediately after the fourth readings, I turning the engine on, removed jack mode, and let it run for a few minutes. The 000284 and C1208A codes had not reappeared, though I hadn't driven the car at all. The car still indicated that normal height was not possible. The height deviations were: -2mm (front left), -3mm (front right), -1mm (rear left), 6mm (rear right). System pressure: 4.6bar (67psi). System air quantity: 94 liters. Strut pressure: front left was 7.94bar (115psi), front right was 7.95 bar (115psi), rear left was 7.65bar (111psi), rear right was 6.92bar (100psi).
Tentative Conclusions
I have spent quite some time reviewing the threads on Rennlist and elsewhere, but admit I have trouble synthesizing the information. My tentative conclusions are:
The compressor is ok. It's definitely capable of operation, since I hear it running.
Theory: While (as I've read elsewhere) the ordinary quantity of air in the system is about 120-130 liters, and this compressor won't seem to get to that point, maybe it's because there is too much leaking from the rear air springs.
But maybe it's just not actually compressing the anymore for some reason, or maybe there's a valve stuck in it, which is preventing the air from actually getting where it needs to go. Thoughts?
The rear left air spring has a serious leak, and the right rear air spring has a smaller leak.
So even if the problem preventing the suspension from raising problem is from the compressor or valve block, these are going to need to be replaced soon anyways.
Maybe the front air springs are leaking, maybe not.
When in jack mode, the front air springs appear to lose a small amount of height--at least that's what the PIWIS is indicating. Does anyone know what the margin of error is on the PIWIS calculated height expectations?
It looks like I'm going to need to replace at least the rear springs, and if I do that, I intend to fill with nitrogen. But if I do that, and there's still a small leak from the fronts, it won't take too long before the compressor is putting atmospheric air into the system again anyways... right?
Maybe there's a problem with the valve block.
Since this part isn't too expensive to replace, maybe I should just go ahead and do it when I replace the struts.
I haven't put the car up on a lift yet to specifically inspect the air springs, largely because I'm hesitant to drive it right now. Any suggestions for further diagnosis?
Your accumulator pressure is low. Get it filled with nitrogen grade 5 see if the car raises, and leave overnight with suspension control off.
The function of the compressor it basically only to transfer air between the struts and the pressure accumulator. Now it it working overtime so be careful that you don’t overheat the compressor.
simple way to check is using an airco tester. Connect low side plug to the pressure accumulator fit it on the high side gauge on the tester and measure pressure in the accumulator.
make sure airco tester low and high ***** are closed else you loose the pressure.
working pressure should be at least 10 bar / 150 PSI
03-01-2023, 12:09 PM
Air Suspension Raising Above Low Level I Not Possible
