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New 955 owner, multiple issues/questions

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So, I finally was able to purchase my dream SUV, with cash.  

2005 Porsche Cayenne Turbo 4.5L  (With Bose audio & nav)  Purchased with 118k miles on it.  Has normal 'family' cosmetic wear in the inside.


I think I have some issues with the software with the onboard electronics.


Headlight washers don't seem to function even after reading multiple posts about it and following suggestions/owners manual.  even checking the fuse. (not really a big deal, I can tackle it last)


One I'm most concerned about is the error code for Over-Boost condition.  Is it the N75 valve that needs replacing?  I don't appear to have any cracked hoses anywhere, no leaks.


The radio seems to lack some functionality and definitely has some software issues.  I'll attach photos.


Air suspension, adjustable dampers, and all other electronics appear to work flawlessly so far, including the low range and center diff lock.


I read all over that these radios are capable of playing MP3 CD's, mine won't.  It does have the DVD drive UNDER the passenger seat.  No CD-Changer in the rear cargo area.

All tools, including the collapsible spare are intact, except the triangles that should be present according to the manual.


Any advice?  I'm doing a PPI this week ( I know, I should have done it prior to purchasing, but here I am) and an oil change because it needs it.


The instrument cluster seems to be missing several informational display options, including current MPG status  (TPMS isn't there because this vehicle wasn't optioned with it)



Any advice and input is appreciated!   I'm not a newbie working on vehicles, I've done my own coil packs/plugs/brakes, & oil changed myself on many of my past vehicles..  But this ride is new to me and one of my two Dream SUVs. (the other was the V10 Touareg TDI)


Don't mind the cracked screen/dead pixels.  CDs play fine, tuners all seem to work.   It will not let me set the date at all, or time zone..  Pretty sure it's a software issue.  I've even attempted the 1-4-8 reset, and watched it re-read each attached device and still gets errors.


LASTLY, there is this device in the front bumper, not sure where it goes to or what it does, but I know it's not stock.


Eventually, I'll be getting rid of that PARROT bluetooth device as it ONLY works for phones, and I'd rather get the module that plugs into the existing harness for the CD Changer to get AUX/Bluetooth/iPod support, later.


Sorry for the long winded first post.  This seems to be a better site than a couple of others I poked around on.


Thank you all for your time!


If my VIN would help, let me know.








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On 5/19/2020 at 11:31 PM, bigbuzuki said:

What code are you getting for the overboost?


The thing on the bumper looks like some sort of radar jammer / light assembly item.


There is also a knob under the kick panel, it has a center volume looking thing, and then a ring around that, that can both be adjusted.  I gotta pull it apart and see if it's part of the Parrot Bluetooth device that's installed.  That thing will be removed, it's junk.


I was thinking on replacing the MAP sensor since it's right on top? and the N75 or whatever since those seem to be cheap.  And while the engine is cold, or rather the oil temprature isn't fully hot, it doesn't seem to pull boost.  Only after everything is nice and hot.



IMG-2834 - OBD.jpg

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Control lines down to the wastegate actuators do crack / split preventing these actuators from opening resulting in overboost condition.


N75 valve and boost sensor on the top of the manifold are also in the loop and are possible suspects.


Below post is the troubleshooting guide for P0234.



Edited by bigbuzuki
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I just replaced my battery as it was sitting at 11.1V after sitting overnight.   I'm fairly new to this Twin Turbo, and don't have a lot of tools on hand (I have a bunch on the list I need to get and some are already ordered)


How exactly do I test the valve for operation?  What's the polarity? or is it marked?


How much of a pain in the *** is it to trace down the control lines?


When I do look at it, for the most part, unless I 'feel' it pulling boost, I see the boost gauge go all the way up to it's 0,9 bar reading..


What do I need to do step by step?  This is my first Porsche, and I want to do what I can to make it as reliable as I can as I plan on keeping it long term.


On the list is the diverter valve upgrade, likely going with the set from APR.  But I have no idea how to get to them.  All the research I've done doesn't seem to net a video or even photos of the process.  I only use quality oil, and premium grade fuel on all my vehicles.  I like things to last lol


I appreciate the help

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Found a guy that did his own diverter valve replacement, I was already considering this "upgrade" as a PM.  Are the lines running to the DV valves what I should be checking?  Or should I be looking at sensors or the threeway valve that's on top?

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So, mine don't make any noise at all.  No honking/screeching sounds.  On occasion, I can hear them bleed off excess pressure, sounds more like a "woosh" and isn't very loud.


I think I'll order the N75 valve, and also pick up an air compressor (as I gave my old one away a long time ago) to see if I can pressurize the lines to see if I can get the waste gates to operate.

I did pull the MAP sensor on top of the Y pipe of the intake. There was oil residue, and I looked down inside with a flashlight and it just looked like a very light coating, and probably nothing to worry about..


Would a Dirverter Valve failure also cause an over-boost condition?


Also, is the valve up front the N75 or the N249?  Looking around at parts, they seem identical. - EDIT:  Never mind, looked around a bunch more and it seems to be part of the EGR system.

Edited by Tecchie
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On 6/1/2020 at 7:19 AM, JFP in PA said:


Bumping posts is not acceptable behavior 😒



I apologize.  Just need some help with this rig.  And for the software side of things also..  Like with the stereo.   I have a handful of little things I gotta put back to normal, like removing the Parrot Bluetooth that was installed, it's junk.  And trying to find the front passenger footwell light wire harness, because I took out the glove box and kick panel and it's nowhere to be found.

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  • 2 months later...

Just curious if anyone had any input on the Radio Firmware issues?  I also can't set the date on the nav unit, I can't even get to the option.  I newly installed a MOST adapter so I can add Bluetooth/USB connectivity to the stock unit (loops into the fiber optics - hooked into the back of the head unit) Everything seems to function - audio wise - but I still get those triangle firmware issues.


The GPS positioning shows correctly on the maps, but the "current location" in the settings menu shows Anacortes WA when that's 60+ miles away from me.



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