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Cayenne TT Error Codes P2404, P0455 - Help Needed


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Hey Ya'll,

I have been lurking on the forums for some time now and recently purchased a 2008 Cayenne TT. I must say, I love the car, drives like a sports car despit 5,000+lbs!

Anyway, recently I had a CEL come on - no changes in the cars behavior, appears to start/run fine.

I borrowed a buddy's code reader and the following codes came back: P2404 and P0455. I believe these point towards a large evap leak. I went ahead and replaced the gas cap with no resolution (I did clear the codes and they returned in 1-2 days).

I wanted to get your opinion on what to do next. I did come across instructions on the replacement of the evap purge valve - should this be next?

Any help would be greatly appreciated. Feel free to leave instructions on how to complete any recommended repair - I am hoping to do this myself.

Thank again!

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:welcome:

P0455 Evaporative Emission System Leak Detected (large leak)

Possible causes:

- Tank cap not tightened correctly, faulty or missing
- Mechanical fault in EVAP canister purge valve (does not close fully)
- Leakage diagnosis pump leaking internally (membrane) or externally
- Mechanical fault in EVAP canister shutoff valve (does not close fully when power is supplied)
- EVAP canister shutoff valve connections leaking
- Tank system (including pipes) leaking
P2404 Evaporative Emission System Leak Detection Pump Sense Circuit Range/Performance
Possible cause of fault:
- Vacuum system leaking
--> The system consists of the mechanical vacuum pump (on the vehicle engine), the leakage diagnosis pump, the intake pipe switch-over valve and, where appropriate, the exhaust flaps in the rear muffler
- Vacuum pump has mechanical fault
- Tank vent valve stuck in closed position
- Purge-air line between tank vent valve and carbon canister blocked
- Short circuit to B+/ground or open circuit in signal line
- Leakage diagnosis pump faulty
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Thanks Loren, I'm trying be systematic in addressing things, starting with easiest to replace/repair to more difficult.

Where can I find the tank vent valve - was thinking to check this out next? Should I just go ahead and replace? Thanks again!

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  • 2 weeks later...
  • 8 months later...

With all leak detection pump operated systems, the engine vacuum (or pump vacuum in this case) is sent back to the leak detection pump, it uses this vacuum and lifts and then releases a diaphragm in the LDP and that is used to "pump" air pressure into the fuel tank. (Yes, they use vacuum(negative pressure) to push and pull a tiny pump and it creates positive pressure...sounds weird but thats how it works!). When enough pressure is built in a calculated amount of time, the system seals and watches the pressure for decay. If no decay, its a PASS and in 2 consecutive passes, (on 2 consecutrive cold starts, not 1) the EVAP MONITOR will complete. If the system leaks a small amount but still holds for a short time, youd get a SMALL leak code. If the system cannot MAKE any pressure, or it makes the pressure but it leaks out too quick to measure, it sets a LARGE leak code.

 

On most LDP vehicles, the pumps rarely fail (older chryslers, 1996-2004 notwithstanding, the old ones actually do fail kinda often)...LDPs dont fail very often. much more common is cracked hoses/lines, loose orings for lines, or a physical leak in the tank area (fuel cap or fuel module seal)...and not uncommon are leaking purge valves up by the intake.

 

The best way to test is with smoke. You can seal off the tank by activating the vent control valve with a scanner or a jumper wire to close the tank vent (exits under the rear fender liner near the fillneck, large rubber hose leaving the LDP and heading to a plastic cylinder that has a filter in it but otherwise is just an exit port). Pinch the hose completely shut with some pliers, of disconnect it and plug it with something tight (a large bolthead or a cork  or similar that fits). Now, the only exit for your fuel vapors is the fuel filler (which should have a tight gascap with a good uncracked rubber seal) and the purge line. disconnect the purge line up front (On gen 2 cayenne its the larger plastic pipe that comes up mid firewall, then has a connector with a release button near the right head, then from the connector it runs down the channel between the valve cover and intake towards the purge valve in the front). When the purge is OFF (not currently commanded to purge!) there should be NO VACUUM IN THAT HOSE, You can tell if the purge is ON/PURGING because the valve in the front will be CLICKING. If there is any vacuum when its NOT clicking, its probably bad. shut off the engine, it should ALWAYS turn OFF. You cannot blow through a closed/off purge valve on any car. So engine off, disconnect the line and see if you can blow through it.

 

If the purge passes make sure you retest it a few tymes, as they can be intermittant and only fail when warm or only leak 1 out of 10 tries and set the light on...then you test it 5x in a row and it always seems to pass but it can still be bad...so test it several tymes before declaring it good(and they actually do fail alot is why I say that.), If it is absolutely good...then comes the smoke testing. ONLY use an approved evap smoke machine. They pump baby oil into a very low temp heater (about 90f degrees) and the baby oil starts turning to smoke. at 90f, there is no danger of igniting gasoline. If you wanna try using a cigar or a party smoker...understand, they are made to use FLAME in a cigar tip...or heaters that get HOT, or temperature dependent smoke sources (dry ice say) which will stop smoking as soon as they traven more than a few feet or which will stay hot and when they hit the gas fumes in the tank...GOOD LUCK!

 

Now that we have the safety points...youd put smoke into the lines heading back to the tank. WIth the vent hose pinched, and smoke put into the PURGE line (The larger line at the firewall with the plastic disconnect button on its fitting)...no smoke should be able to get out. NONE. Not even a small wisp...it is only good if its NONE. If any smoke comes out, find it (flashlight helps) and fix it! bad line, bad Oring, bad tank seal...whatever...find and fix.

If no smoke comes out...and if you have a flowmeter on the evap smoker (most do) and it says no flow after a minute or so...you have no PHYSICAL LEAKS. Now you look for MECHANICAL LEAKS. IE - something that is supposed to seal when told to to create the pressure...and isnt sealing to allow the pressure for the leak test to reach required levels. If the LDPs vent solenoid is the leak (it can be)....the smoke will exit the vent line even though its closed with the scantool or activating with a jumper wire...but would stop when you pinch the hose closed with needlenose pliers. If you dont have a scantool and cant figure out the jumperwire idea...then check VACUUM. The SMALLER hose heading back from the intake...its a vacuum hose, it doesnt have a button release like the larger hose...and it comes out the center of the intake, then makes a big horseshoe turn rught by the top center of the firewall before clipping into the bracket and heading down and back side by side with the larger hose that feeds the purge line.  Yank it off of its plastic connector (its simply pushed on) and put smoke in IT back to the tank, if your flow check shows no flow after a few seconds...its not leaking. If it shows flow, or you see smoke...find and fix. straight forward stuff as discussed above. If it is NOT leaking, now you wanna measure vacuum at the vacuum line which goes to the vacuum pump. In most cases, simply idle the engine and pulle the vacuum hose off. The pump on the right head always makes vacuum when the engine is running. That hose is connected to it, so you should have good solid constant vacuum on it. if there is no vacuum...then the pump isnt making vacuum or the line is off or pinched. If the pump has failed...youd have no vacuum to anything on the car that uses vacuum...IE power brakes! So if the car also has brake problems...you likely have your answer.  If the brakes are perfect and you ONLY have a p0455, then id check to make sure the vacuum to the LDP in that smaller line is stable and present and over 10 inches. Remember, a LARGE LEAK code is set when pressure leaks out so fast it cannot be measured as holding at all. However, if no pressure is ever even created (like that small hose being broken or disconnected so the LDP never makes any pressure or the vacuum pump being bad)  the PCM doesnt know the difference and will call it a LARGE LEAK when in fact the problem was the vacuum to the LDO was never applied to begin with...and the fuel tank system in fact has NO LEAKS. 

 

Hope it helps. And yes, this logic applies to all LDP evap vehicles with some small mods in scanner control and locations of lines. But the above works on a 2008 cayenne specifically.

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:welcome:

 

P0455 Evaporative Emission System Leak Detected (large leak)

 

Possible causes:

- Tank cap not tightened correctly, faulty or missing
- Mechanical fault in EVAP canister purge valve (does not close fully)
- Leakage diagnosis pump leaking internally (membrane) or externally
- Mechanical fault in EVAP canister shutoff valve (does not close fully when power is supplied)
- EVAP canister shutoff valve connections leaking
- Tank system (including pipes) leaking
 
P2404 Evaporative Emission System Leak Detection Pump Sense Circuit Range/Performance
 
Possible cause of fault:
- Vacuum system leaking
 --> The system consists of the mechanical vacuum pump (on the vehicle engine), the leakage diagnosis pump, the intake pipe switch-over valve and, where appropriate, the exhaust flaps in the rear muffler
- Vacuum pump has mechanical fault
- Tank vent valve stuck in closed position
- Purge-air line between tank vent valve and carbon canister blocked
- Short circuit to B+/ground or open circuit in signal line
- Leakage diagnosis pump faulty
 

 

And with regards to the original post, which I hope is already fixed (just posting all this because Im new and have been doing evap for 15 years all makes but porsche lately) since this had a pump sense circuit in addition to large leak...Id generally start with pump diagnostics (does it turn on/pump when commanded?) and is it getting vacuum (the small line). If its getting vacuum (remove the small line at the pump when running) and it cant see it...pump is bad. If there is a problem with the pumps diaphragm leaking internally so it never moves despite vacuum...same issue, bad pump. If its pumping like a champ...but the vent is plugged solid as loren said, it will still see itself as bad. (most cars dont measure pressure for anything by the tank itself, they dont know how much PRESSURE anywhere else in the system, they see the CHANGE as indication that it worked. pressure change on/off switches are much cheaper to make than pressure measurement sensors that can record exact amounts).

 

TYPICALLY, in most diagnostics post 2000, when a code uses the word CIRCUIT, you are chasing something electrical that isnt changing as expected or isnt showing proper voltage/ground as expected even when not active. unplugged stuff sets a CIRCUIT CODE.Shorted wires set CIRCUIT codes. leaking hoses set LEAK codes or PRESSURE codes. RANGE codes are the factorys way of saying IT COULD BE EITHER, SINCE A LEAK WILL SHOW SENSOR VOLTAGE THAT ISNT WHERE WE WANT IT, BUT ISNT SHORTED....but they like to hedge so they say RANGE. It means its likely electrical, but dont rule out a leak entirely and look at the electrical values if you have a tool to do so.

 

So if you get a code that says PURGE CONTROL CIRCUIT, or LDP CIRCUIT, the 1st thing I check is the component is plugged in, and the wires going to it arent broken down or oil soaked. IF they look good, most solenoids are 2 wires, 1 a constant hot of 12v, the other a switched ground from the computer to turn it on or pulse it on rapidly to control flow. Evap solenoids almost always are pulsed...hence why they CLICK when they are working...they dont stay open or closed because that is uncontrolled flow. By pulsing at different amounts, they can open it 50% of the tyme or 70% or 20% and regulate flow. If the circuits function, and have power and ground (on or pulsed), then start checking for leaks as described above. It will be there.

 

Also be aware, you can set circuit codes quite easily while testing. Unplug anything that is constantly checked (most components on newer cars) and check codes immediately...code is instant...even if you plugged it in 1 second later and its reconnected. Just clear the codes and if the code comes back instantly, its broken internally, bad wiring, or bad computer. circuits are constant...they are plugged in and work. Or they set codes.

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  • 1 year later...

Thank you for the huge post, very informative !

Another sad story from a long time forum lurker, with a 2008 Cayenne TT

I have the same (ish) problem, symptoms include:

-P2404 & P0455  

- Puff of smoke on start up (every 2-3 days) 

-In addition I'm seeing an occasional (once every 2 weeks) idle drop & engine vibration when coming to stop. 

 

 

I have a smoker & the Durametric cable to perform the diagnostics but can not find where you activate the purge valve with the scanner (if anyone knows that would be great!?)

 

Checked the gas cap for seals tightness, cleaned it up, looks immaculate, 100% isn't the cap after the smoke test  

 

Pulled the purge valve connection& can not blow through the purge valve at all when the engine is off. 

 

Opened up the rear wheel well & inspected the Evap canister, which looked good but there is engine oil all around it, Pic attached. looks like its seeping out from the connection between carbon canister & the LDP. 

 

Performed smoke test any way & zero leeks not a puff until i opened the gas cap to confirm the tank was full of smoke, it was. 

 

Pulled the carbon canister to access the LDP connection & i found that the electrical connector was filled with oil. Connected a 12v jumper & can hear the solenoid click but in any state or polarity it passes smoke. i have ordered a new LDP diagnostic pump but would like to know: 

 

How the heck did engine oil get to the back of the car ? 


 

thank you in advance. 

 

 

 

IMG_9372.JPG

Edited by roach2012
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After looking at a few more diagrams there there a couple of options but i don't really understand any on them fully. 

 

1 - its back flowing through the vacuum line (which was also full of oil) , kinda posable given that this is a turbo but I'm not sure on how exactly the pressure would get reversed. The positive pressure at the LDP solenoid could explain the electrical plug filling with oil though. There is a good vacuum in the crank case when the engine is running & the oil filler cap is removed, not likely a vacuum pump issue.  

 

2- coming through the carbon canister but how would oil get in a carbon canister ? maybe the purge line ? 

 

Are there any other possibilities ? 

would anyone know what to look for regarding likely failed components ? 

 

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5 hours ago, roach2012 said:

After looking at a few more diagrams there there a couple of options but i don't really understand any on them fully. 

 

1 - its back flowing through the vacuum line (which was also full of oil) , kinda posable given that this is a turbo but I'm not sure on how exactly the pressure would get reversed. The positive pressure at the LDP solenoid could explain the electrical plug filling with oil though. There is a good vacuum in the crank case when the engine is running & the oil filler cap is removed, not likely a vacuum pump issue.  

 

2- coming through the carbon canister but how would oil get in a carbon canister ? maybe the purge line ? 

 

Are there any other possibilities ? 

would anyone know what to look for regarding likely failed components ? 

 

Open purge valve with the associated check valves leaking on the way to the intake could push oil vapors back to the evap canister when under boost as it pushes back up the pipes? My only logical guess.  Would normally produce a p0441 code I think? 

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That code from another Porsche board points toward the vacuum pump.  I have an 08 GTS and have the P2404 code right now.  Another poster on the other board had that same P2404 code and just changed his vacuum pump and so far the code has not returned.  Everyone that had the P2404 code on the other board that changed their vacuum pump saw the same results (code not returning).  I am about to replace my vacuum pump, also, to get rid of my recurring P2404 code.

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Thanks for taking interest,

In this case after testing the LDP the P2404 code was set by the leak detection pump when it was full of oil possibly form engine blow-by of some kind (bad check valve or bad engine TBD) Either way the oil must have been on/around the reed switch causing an electrical fault & a bad signal (oil is conductive &/or just sticky) , it seems to have cleared up after draining. Still have P0455 though.

 

Currently waiting on LDP delivery from an online supplier. 1/2 to 1/5 of dealership price depending on which you call VW/Audi/Porsche, all our EVAP systems seem to be exactly the same. I have also ordered a couple extra check valves to place on the vacuum line just upstream of the LDP to stop the back flow of oil. If this fails over time there is space in the wheel well for a small catch can. 

 

The vacuum pump seal could very well be the source of the oil, but it is currently generating the 19 InH20 pressure at the LDP which is plenty & a healthy whooshing sound if i open the oil cap. I think the real solution if that is the case is to address the blow-by in the engine.

 

 

so to date :

P0455 Evaporative Emission System Leak Detected (large leak) Possible causes:

 

1- Tank cap not tightened correctly, faulty or missing- ---- Nope 

2- Mechanical fault in EVAP canister purge valve (does not close fully) ------ Nope 

3- Leakage diagnosis pump leaking internally (membrane) or externally ---- Posable,  EVAP side not leaking but oil in the electrical plug means there must be some communication between the vacuum line & the atmosphere, shouldn't directly cause a P0455 though. 

4- Mechanical fault in EVAP canister shutoff valve (does not close fully when power is supplied) ---- Posable

5- EVAP canister shutoff valve connections leaking --- fixed 

6 - Tank system (including pipes) leaking --- nope 

 

just a note i think 3,4,5 are all the what is sold as the LDP 

 

 

Would anyone know there the vacuumed air goes to after the vacuum pump? 

& would anyone know how to trigger the Evap self test, i'd like to see if the canister shut off works with a smoker. 

 

 

 

 

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  • 4 weeks later...

Kino, you could be right. 

After replacing the LDP the code went away for a week or so & has now come back twice. Are there any good DIY's for replacing the vacuum pump ? i see one on Pelican parts but i appear to have an extra metal line for the hydraulic sway bar completely blocking access to the lower bolt. 

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  • 1 month later...
On ‎10‎/‎31‎/‎2016 at 11:59 AM, roach2012 said:

Kino, you could be right. 

After replacing the LDP the code went away for a week or so & has now come back twice. Are there any good DIY's for replacing the vacuum pump ? i see one on Pelican parts but i appear to have an extra metal line for the hydraulic sway bar completely blocking access to the lower bolt. 

 

Well, my P2404 code went away when I changed the vacuum pump but my P0455 codes still remains.  I don't know it could be.  Replacing is no that bad.  You do have to work blindly for the bottom bolt.

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Yeah that lower bolt was a pain, especially with what i think is the steel PDCC line over it. Ended up giving it to a mechanic to fix, which to their credit they did well.   

there may be oil in your vacuum line to the LDP left over from the failing vacuum pump, un-hook it at both ends & blow some air through fixed that on mine (after also replacing the LDP)

 

All codes gone now but still getting large puff of smoke on start up (every 2-3 days) & an occasional large puff during acceleration. 

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roach2012,

 

Are you referring to the P0455 code?  So, I should unhook the LDP and blow some air through the LDP?  You have a TT.  I have a GTS.  I don't know if that even makes a difference.  What side of the rear of the vehicle is the LDP?  Looking at your pic above, where is the LDP in that pic?  I am a DIYer as I know how to follow directions.  :-)  If you can tell me what I need to do to actually pull the LDP and then blow air through it.. I am game.  Is it hard to do? 

 

Also, are you saying that you replaced your LDP thinking it was bad but all you had to do was blow some air through it?  If so, I wouldn't have known that either.

Edited by kino1161
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I believe the all the Cayennes & Panameras have the same evap system, along with the bigger Audi's & VW's (i found this info on a VW site).

When i replaced the LDP, it & the vacuum line were flooded with oil (i now know this was due to the failed vacuum pump as you pointed out). But the oil did stop the LDP from even performing the test, subsequently triggering P0455. 

 

To clear the line there are some good tutorials on how to get to the carbon canister assy, but this is what i did:

- unhook vacuum line in engine compartment

- jack up rear right side

- remove rear passenger wheel

- remove wheel cowling 

- look up & un-hook carbon canister 3 x bolts

- un hook the vacuum line, the smaller pipe going in to the top (solenoid part) of the LDP

- blow air in from the engine side (used a small electric air bed inflator)

- wait & see what comes out. 

 

I'm still not sure if you can salvage an LDP once its flooded with oil could be worth a try if you can pull it apart. When its working normally you should be able to hear a clicking sound as it opens & closes. 

 

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Sorry, for all the questions.  Which vacuum line in the engine compartment are you unhooking?  Are you blowing air in from the engine side of the LDP right there in the rear of the vehicle where you unhooked it or are you actually going to the engine compartment and blowing air from there and if so from where?  How were you able to blow air in with an air bed inflator?  Is an air compressor too much?  If the LDP is good, there should be no oil coming out and only air, correct?  If oil does come out, then it is bad?

Edited by kino1161
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  • 2 weeks later...
  • 8 months later...

I recently got a '06 955S.  Discovered a serious fuel leak under the left side where one of the fuel pumps reside.  I took it back to the dealer, still under warranty, and along with a faulty right side head light housing which kept coding and a safety brake code they happily fixed all and replaced the fuel pump.  However, ever since then I continuously get the CEL with the EVAP EMISS LEAK (SMALL) code.  I have taken it back to the used car dealer five times now.  They have each time, happily taken the car, and given me a fabulous loaner but I am frustrated as I have been paying on a car for over three months now and have only had actual possession just a 1/3 of that time.  I'm grateful they are willing to continue to work on the car but when do I call it quits and insist they take it to a genuine porsche repair shop.  My shop recommended I push to have the dealer fix it since they did the fuel pump work in the first place but, seriously, this is getting old.

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1 hour ago, Sandia955S said:

I recently got a '06 955S.  Discovered a serious fuel leak under the left side where one of the fuel pumps reside.  I took it back to the dealer, still under warranty, and along with a faulty right side head light housing which kept coding and a safety brake code they happily fixed all and replaced the fuel pump.  However, ever since then I continuously get the CEL with the EVAP EMISS LEAK (SMALL) code.  I have taken it back to the used car dealer five times now.  They have each time, happily taken the car, and given me a fabulous loaner but I am frustrated as I have been paying on a car for over three months now and have only had actual possession just a 1/3 of that time.  I'm grateful they are willing to continue to work on the car but when do I call it quits and insist they take it to a genuine porsche repair shop.  My shop recommended I push to have the dealer fix it since they did the fuel pump work in the first place but, seriously, this is getting old.

Sounds like this issue only presented itself after the fuel pump was replaced?

Open and replace both Rubber gaskets (labelled as seals number 8 on the diagram) on the left and right side filter and regulator respectively, would be my first and most inexpensive thing to try if DIY and no other ideas. The rubbers are very tricky to refit even when new but a helper will make it easier to get it seated properly and not leak. 

Also the vent pipes to the tank fittings can get damaged by some enthusiastic mechanic work, so consider that as well. 

 

Screenshot_20170901-235418.png

Edited by lewisweller
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  • 1 year later...

On my Porsche Cayenne 2009 GTS got code P2404.  After reading all the blogs, replaced the vacuum pump.  It was the correct decision.  Code went away and car runs better.  You can change yourself if you have time and patience.  Pump costs $160 online.  Tools you'll need is small ratchet (https://www.amazon.com/Drive-Dual-Stubby-Ratchet-Handle/dp/B009TA14P2), E10 socket, string (attached to ratchet cause you'll drop it trying to squeeze it in position so easy to recover if you drop it), plier (disconnect the hoses).  Pelican Parts website has good instructions on pump removal.  Don't need to remove the intake manifold if you can squeeze hands where vacuum pump is located.  Maybe an hour job.

Edited by HarryRhee
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