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There are a few threads on here and 6 speed and renntech that basically go like this:
I got the "not possible" error when trying to raise my suspension.
I got chassis faulty.
I got chassis failure.
My suspension droops when parked.
I came back to my car and it was lower than when I left it.
I had a leak in an air strut.
I had a bad compressor relay.
I had a bad compressor.
My durametric is useless for troubleshooting level control.
Which icarscan icarsoft ebay obd scanner helps troubleshoot level control?
The 958 air suspension is a closed system. It is filled with unicorn farts available only at the dealer.
I took it to the dealer a million times. They were unaware of the unicorn farts or were out of the N5 unicorn farts bottles.
It cost $12,000 at the dealer to fix and it still doesn't work.
I traded the car in.
I fled the country and now live in a tent in the wilderness.
Not a lot of DIY material nor actual solutions.
I am in the midst of this issue. I am three shocks (both rears and the front right), a compressor relay, and a compressor deep into this garbage. Currently something is blocking the compressor from physically turning, but electrically the compressor will run just fine if the lines are disconnected. I assume I'll be purchasing a valve block next.
Here is what I have learned so far:
The struts are expensive. Bilstein makes slightly less expensive ones. So far they fit okay but they are constructed differently.
The compressor is stupid expensive. Some place called RMT sells continental ones that are exactly the same as the Porsche ones.
The system is not entirely closed. It has an accumulator (just like the first gen does). It also has an intake from ambient air and an exhaust to ambient air. The difference is that when the system releases air from an air spring, it pumps it back into the accumulator instead of just venting it to atmosphere. It will still suck in ambient air to supplement the amount of air available in the system in order to compensate for leaks over time. There is a fitting to charge the accumulator with a porsche special tool. The shop manual does say to fill it with dry nitrogen only. This is good advice.
The compressor relay is underneath the dash. You have to remove the trim piece above the pedals (that has the footwell light) and look up to see it. There is a torx screw, like a t30, that you can undo and the whole panel comes down. Each relay socket has a number cast into the plastic mold. Socket number 1 is the compressor relay. The relay can burn out from a compressor that runs too long (due to leaks).
The fuse is one of those huge 40A orange ones, on the left side of the dash, number 56.
When I do finally defeat this, I will make some sort of DIY. Best I can tell, this repair isn't really possible without the help of a shop to recharge the system after it gets too low (I don't think the compressor will pump it up enough with ambient air on its own).
I'll be very interested in hearing what resolves your issues. What I'm not certain of is the sealed system. If I understand you correctly - the gas in the system is returned to an accumulator instead of venting to atmosphere. You then state that the accumulator has an air vent on it? How is that vent controlled? Is it possible that the accumulator is actually a rubber-bladder storage tank? One side goes to the system, and is sealed from the other side (going to air) by a rubber bladder? That would make the system sealed but also able to allow for pushing the gas back into the accumulator without losing it to the atmosphere. I'll have to look at my AllDataDIY and see if there is any explanation.
I assume you've replaced the 3 suspension bags? Or was it the entire strut assembly?
I think I'll subscribe to this thread - I think it will be interesting. FWIW - the iCarScan that I have does have functions to calibrate the 958 suspension height. I just went to take a look at what version I have and it's asking me to download V5.5.7 of EZDiag. My old version was probably V5.5.5 - I have some things I have to do this morning, but sometime this afternoon I'll download it, hook it up and see if the functions are still there. So far I haven't seen them remove any functions on updates.. The top-level software appears to be called "GoloMasterDiag3.0"
The “accumulator” i believe is just a tank. Like you, when I think of an accumulator I think of a cylinder with two separate fluids and a bladder in the middle. It could be that way but I don’t think so.
To answer your question about it being semi-open, there are check valves. Basically the pneumatic circuit is such that he pump takes suction on whichever is a higher pressure- the air coming from the accumulator or the atmosphere. Normally it would be the accumulator. At some point I would like to draw this all out as well.
the valve block has solenoid-operated valves that let air into or out of each bag and the accumulator.
I replaced the entire strut assembly on each of the 3 I did. Didn’t make sense to keep using dampers with 80k miles on them
Thanks for taking the time to explain your experience. My suspension seems to work well, but at times the compressor seems to run a long time. Particularly when at high elevation. I will watch this thread too.
We had an issue driving north of the Arctic Circle with temps down to -36F. Got a chassis fail light but no change in drive-ability. Two miracles then occurred - first somehow we got cell connectivity and then our indy shop called us. Troubleshot over the phone which pointed to moisture getting into the system then freezing. Lucky we had passed all the technical sections of our 5,500 mile one way trip and continued on at 'normal' height. Will have dig out what was replaced when we returned to the lower 48, will be a while as our house is in disarray as a re-muddle is in progress.
Subscribed to the thread.
____________________________ https://rennlist.com/forums/cayenne-...meet-otis.html
Last edited by RS-America; 09-25-2018 at 02:50 PM.
Reason: format
The “accumulator” i believe is just a tank. Like you, when I think of an accumulator I think of a cylinder with two separate fluids and a bladder in the middle. It could be that way but I don’t think so.
To answer your question about it being semi-open, there are check valves. Basically the pneumatic circuit is such that he pump takes suction on whichever is a higher pressure- the air coming from the accumulator or the atmosphere. Normally it would be the accumulator. At some point I would like to draw this all out as well.
the valve block has solenoid-operated valves that let air into or out of each bag and the accumulator.
I replaced the entire strut assembly on each of the 3 I did. Didn’t make sense to keep using dampers with 80k miles on them
I'd love to find a diagram of the air suspension system. AllDataDIY doesn't have one that I can find. I'll spend some time poking through the 11,000 pages of factory manual and see if anything shows up.
Meanwhile - off to the garage to see if iCarScan still has the suspension calibration functions available for the 958...
Took a snapshot of the air-suspension (aka Leveling) page in iCarScan. There are also pages where you can read live data. Those work, although what some of the pages are telling me are a tad confusing..
I did not try any of these functions since my system is working and I don't want to screw it up by screwing around with it.. so I can't say for sure if they all work or not. If anyone wants to play sometime - perhaps someone under warranty - we could explore some of the options here if you can get your P!G to the NJ shore area for a few hours.
the codes I had remaining after changing the compressor were 1E1 and 1D1 which both pertain to the "switch over valve"
Plugging the new pump in would cause "chassis failure" immediately while the old one would not. Neither pump would actually run on the car, but both would run when jumped with a battery to the motor leads.
The "changeover valve" referenced in 1E1 and 1D1 codes is the valve that's on the forward end of the compressor/valve assembly. The compressor is really several parts: the motor, the pump/heat sink, the dessicant/filter canister, and then the changeover valve assembly and manifold for the tubing connections.
Long story short, after some troubleshooting I discovered that the changeover valve on my NEW Continental pump (not rebuilt, per the advertising) was faulty. My old pump the motor/pump was worn out, and on the new one nothing would run because the changeover valve was throwing codes and "Chassis Failure" immediately.
So tonight I'm going to install my old "good" changeover valve onto the new pump and motor to make one good unit. I will, of course, be seeking a warranty replacement but I can't have my car sitting on jackstands any longer while I sort that out.
The only remaining level control / PASM code is 852 / 354, which I have yet to decipher.
The system is intended to run on nitrogen alone as a closed system until the system pressure and/or volume is detected as below a certain threshold. Once below that threshold (because of a leak somewhere in the system) it has the ability to pull in atmospheric air to utilize with the idea that atmospheric air is better than nothing! If your system is newly filled with nitrogen, it should not have any chance to freeze the desiccant like the older generation 955/957s. But over many years and miles it is likely that it has reached the point of utilizing atmospheric air which will more readily introduce that problem.
I imagine the dessicant freezing was an issue for all the cold-weather people. I bet a LOT of cayennes were purchased new in New York and then subsequently had freezing issues. Not really an issue here since the coldest it gets is 65F.
I have been taking some photos. It's hard to stop and document along the way so I'll probably do some recap photos once I have it all figured out. Maybe make a short vid.
And garrett is correct; it has the ability to take in atmospheric air, but it shouldn't ever need to unless there is a leak. Or if some bozo takes the whole system apart, like me.
Once I'm done, I intend to do a system purge and refill with dry nitrogen.
I spoke on the phone with "the retailer" who sold me the "new" Continental pump. Now I will say this. It was much cheaper than the Porsche one. The pump looks IDENTICAL to the Porsche one. Even the label is the same, sans the P logo. The only difference I noticed was that the insulation on the two sets of wires (two wires for the main motor, three for the changeover valve) was fancy heat sleeving on the original one, and plastic wire loom on the new one.
During my phone call I discovered that, underneath that loom, there are some solder joints. The retailer who shall remain unnamed apparently gets these continental pumps with either no plug, or some different plug, and then solders on a Porsche plug so it'll fit the cayenne. Which would be just fine, except they didn't connect one of the changeover valve wires.
This explained why the new compressor was dead immediately and throwing "Chassis Failure" as well as codes 1E1 and 1D1 as soon as the ignition was turned on- there was an open circuit on the changeover valve and the car knew.
Once I soldered it all back together, I reset the battery for ten minutes, got the car reasonably level with my floor jacks, hooked up durametric, closed the doors and hood, locked the car, and cranked it up.
There was much confusion and the compressor ran a bunch. No faults at first. The car recognized it was in some sort of lower-than-low level. Eventually I took mercy on the car and shut it off and disconnected the battery again. I was finally able to fully remove the floor jacks and the car at least stayed somewhere around loading level underneath its own air pressure.
After some waiting, I plugged the battery back in and cranked back up. I had code 354 remaining at first, but as the car finally got back to low level, that code cleared itself. I was, finally, PASM code free. I drove around the neighborhood in low level, however the compressor was turning on for a few seconds, then back off, then back on, pretty much constantly. Eventually chassis failure came back on, but after a minute it cleared and the compressor started back up again. I shut the car down to keep it from running the compressor too hot.
09-25-2018, 10:33 AM
Air Suspension Not Possible : I will defeat it.
