panzer_pig

I've done my best to see if I could find relevant threads and despite finding a few I didn't see any with my particular error code and many stated attempting some fixes but never returned to say what worked or if they still have it. I hope to solve my issue and document the fix well to help others.

Description of problem:
I have a 2008 cayenne turbo with PDCC and I'm getting the "WARNING CHASSIS SYSTEM" error which happens quite often under a variety of situations with some level of reproducibility.
Most often is I'll be turning left, I hear a slight clunk of the sway bar going slack or the pump shutting off and the warning shows up on the dash, the sport button is disabled, and the car leans since the PDCC isn't working.
The error on the dash clears itself after restarting the car but the code is stored in the module, sport button is enabled and PDCC works until the next time the issue happens.
I've pulled the error code 15527 "pressure build-up FA insuff" from the PDCC ORS module.

When does it occur:
Often when I'm making a left turn, even a relatively gentle one at <15mph. It isn't consistent though, I've gone a week with no issues, driving the car on tight twisty roads up in the hills. I've also had it happen driving in a straight line doing 5mph in a parking lot where there is no way the PDCC should even be under any kind of strain.
It seems to happen more when the car is relatively cold but it has happened after turning the car off, going into a store and driving it again 10 minutes later.

Fixes attempted:

1. Took it to the dealer, they couldn't reproduce the issue, they flushed the fluid and replaced both the PDCC and power steering reservoirs anyway per my request. This didn't fix the issue, it happened again a day or two later.
2. I took it back to the dealer intent on reproducing the problem myself and the car of course refused to behave, they were later able to reproduce it after letting it sit and trying it with the car cold. They called Porsche who recommended they replace the PDCC control unit (~$700). This appeared to work but a week later the issue was back.

Thoughts:
This happens most often while I am turning left which makes me think that one of the sensors might be going bad or there's a sloshing effect.

I don't think there's a fluid leak or anything because the PDCC works well some of the time and the reservoirs aren’t low after the last fluid flush.

I don't think there's an issue with the tandem power steering pump because the steering wheel never feels heavy, but I don't know for sure. It does seem to make sort of a strained noise when I'm turning and have the window down but that could be normal (not the normal cayenne PS pump whine but more of a hissing noise although it doesn't exactly sound like a pressure leak). Maybe I will need to mount a gopro under the car and drive around... If I do need a new tandem PS pump I think they're about $1100.

The dealer said that if it was a sensor going bad we would need to replace the valve block (~$1600 + labor + fluid flush) but no guarantees this would fix the problem. That's a lot of money to sink into something without a guarantee that that's even the root cause.

Does anyone have any ideas about what could be wrong or how to go about nailing down what's wrong? Is it possible it’s a distribution solenoid like in this thread? https://www.6speedonline.com/forums/...is-system.html

I looked today and didn't see any obvious leaks or fluid anywhere in the hydraulic lines or near the tandem pump.

J'sWorld

It is called a work flow. You educate yourself on exactly how the system works, learn about all the components that make up the system, the subsystems that are tied into the PDCC...etc. Then you start at point a and move all the way through to point z. Then you develop hypothesis, theory, and a diagnosis. Then you start wasting money by throwing parts at it based on all the above. Im sorry I cant answer your question directly. You aren't going to find a real answer here because 95% of Cayenne owners do not have the diagnostic software/hardware/data logging capabilities, techinical information, or want to figure these complex problems out.

Find a mechanic that is willing to diagnose the issue correctly, doesnt get angry when you call them out on how they arrived at their diagnosis, and is willing to meet you halfway when thrrowing a part at it doesn't remedy the problem.

user 83838290

The tandem pump failed on my wife's 08 CTT after a gasket failed and dumped all the fluid over our driveway... and the strering was always okay. I had to replace (or refurbish, I don't remember) the pump and I also had to buy the front swaybar. No issues sisnce then.

PDCC is pretty complicated and has to be done by someone who knows it at least a bit. I would not count on the dealer to know their stuff other than throwing parts at it. Find a mechanic that works on cayennes or audi RS6, they have a similiar system that fails from time to time as well.

panzer_pig

Thanks Mr. Haney, you have a good point but I still think in the interest of helping other people and documenting the issue I'd like to get this some visibility and maybe more people will chime in with suggestions or how they fixed/went about diagnosing similar issues. I think I have a good understanding of how PDCC works but not how it tends to fail and there are only a handful of posts about issues with it where there isn't something obviously catastrophic happening like a burst line.

I don't want to take it to a shop after my experience with the dealer since their approach was pretty much to just replace parts until it's fixed which is just unacceptable since you have to flush the system every time you replace a component (or maybe that's just what the dealer told me).

I have the parts catalog for the car and can see how the system is all hooked up. I got under the car and looked around the sway bar, checked some of the hoses and the reservoirs and didn't see any leaks. I've only taken off the engine under trays though, so soon I'm going to take off the wheel/wheel liner to get to the valve block and hopefully be able to see more. From what I can tell it looks like it's behind the (LHD) passenger side wheel well liner where input pressure hoses go into the block from the tandem pump on the other side of the engine and go out to the distributor and on to the swaybar.

Lupo, thanks for the heads up. It's good to know that your steering felt fine until the pump died. It is possible my pump is just dying because I recently hit 100k mi/10 years old, and the warning is about insufficient pressure. I only wish there was some way to test the pump without just replacing it but my dealer told me there isn't any way to do that.

Maybe I'll figure it out but if it's not something obvious I think the safest and easiest way is really just replace everything, pump, swaybar, valve block, possibly even hoses (to get the updated ones with the rubberized exterior rather than the old braided steel ones). That way I can just do one flush and hopefully not have to replace any part of the pdcc for another 100k miles, but that is well over $3k without labor and I'm afraid even with all of that there's a chance it won't be fixed.

J'sWorld

Best thing is to find good indy with a PIWIS. Even then knowing how to work that thing is lesson in itself. It is a powerful tool in the right hands.

user 83838290

Hey, just to be clear.: even with PDCC reservoir empty and the PDCC part of the pump being dead, power steering works just fine. I drove it around waiting for the sway bars and had 0 issues other than the car leaning into curves.

Petza914

I think you can also get chassis system failures if you have a problem with the air suspension. I may be incorrect, but thought I'd mention it just in case you have a different issue that's tripping the message. Does the height adjustment of the air suspension work all the time, evenly at all 4 corners, and relatively quickly?

panzer_pig

That is good information, thanks Lupo. Since they're independent and the power steering pump works fine I think it might just be the PDCC side of the pump that is maybe dying on me, that would make sense for why it doesn't think it can get enough pressure, it's weird that the system works fine sometimes though..


Thanks for the suggestion, I've heard that as well. When the dealer pulled the code for insufficient pressure buildup they said the module it was pulled from was PDCC/ORS so I assume that mean's it's PDCC and not air suspension related.

Height adjustment works fine, yesterday I went from the lowest setting to the highest, sat for a while, then turned it back on and went back down to low, no issues.

Dr97ft

Hey check out my post carnival ride on page four, or maybe on page one, now I updated again. Sounds similar at least. Hope it helps

Twintipin13

Any updates on this?

Twintipin13

@lupo.sk Would driving the vehicle around with the pdcc reservoir empty cause any problems? Or is it fine to drive until I am able to get the pump fixed?

user 83838290

If the reservoir is empty, the pump is shot so I don't think you can damage it any more... I drove it around a week before it went to the shop and the pump could still be refurbished

Twintipin13

@lupo.sk Thanks for the speedy reply. Do you remember approx how much it cost to refurbish?
Also, since the PDCC has nothing to do with the air suspension, I should be able to drive in any ride height/comfort mode correct?

user 83838290

Sorry, I don't recall the cost, check my thread (should I buy it - 08 ctt), it might be there somewhere.
And yes, you can still control the height and comfort mode

playskool1

panzer_pig - I've had the same issues as what you've described in your first post ever since I bought it. The warning light didn't trigger until a month later. The chassis warning light sometimes doesn't turn on for weeks and sometimes it can happen twice in one day. A simple restart of the engine clears it and functions as normal

During left hand turns, do you hear a slight pop sound at the front right suspension area and notice the car is not driving leveled? After the engine restart, the car is level again.