Boost Leak Dtc P2281 Help?

[Reborn996]

Okay, it seems I have a boost leak after putting in the new diverter valves. At first I thought the install was messed up but I rechecked everything and it is good and tight. I also put in new sealing rings on the lower boost hoses to the intercooler as the drivers side one was removed for the install and was coated in oil. The o-ring did look a little worn but even after replacing it I still have the error code under high boost. My theory is that with the new EVOMSit software and diverter valves (the old valves would not hold full boost) once the engine saw the higher boost it developed a leak somewhere.

What is the best way to troubleshoot this? I checked the diagram for the boost hose system and it has an unbelievable amount of o-rings... would hate to have to take the whole thing apart to replace them all.

[PTEC]

There is a factory tool for checking for boost leaks. Its basically two metal plates that fasten to the intake pipes with locking pins similar to what the air box uses, one plate for for each side. One of the plates has a tire air valve that you can put pressurized air into the intake system. If you have a leak you can hear air hissing out of somewhere. I'm not sure where you would find this tool except for at a dealer.

Yep thats them pictured below.

Edited April 13, 2010 by PTEC

[Loren]

US MSRP $196.17 -- I'm sure the folks at Sunset Imports (Porsche Parts at Dealer Cost) can do better pricing.

[Reborn996]

Let me see how much my local dealer will charge to check this for me. Might just be worth buying it if the diagnosis is more. LOL

[Reborn996]

Okay, I replaced the boost sensor, all of the o-rings, and rechecked all of the hose connections... but still have this dtc coming up! :( I noticed it is boosting to .8 bar and everyone who has checked it does not hear any boost leak and says it pulls fine... so, my logic is telling me I might have a sensor error rather than an actual boost leak (which is why I replaced the boost sensor). Could it be my MAF? Would I get this P2281 code if the MAF was not reading right?

Hopefully my local Porsche dealer will get the regulator needed so we can do a full pressure check with the above tool... LOL

P.S. Not sure of it helps but I noticed each time this happens I get a PSM warning on the dash.

[Loren]

P2281 Leak Ahead of Throttle Valve – Below Limit/Above Limit

Possible cause of fault:

- Leak between turbocharger and throttle valve

Check intake distributor for leaks.

[Reborn996]

Intake distributor... do you have a diagram that shows where this is? If you mean the y-pipe in front of the throttle body I replaced that o-ring as well when I did the boost sensor replacement. No cracks in it that I could see. It has to be before the throttle body in order to throw this code right?

[Loren]

Intake distributor... do you have a diagram that shows where this is? If you mean the y-pipe in front of the throttle body I replaced that o-ring as well when I did the boost sensor replacement. No cracks in it that I could see. It has to be before the throttle body in order to throw this code right?

Item 3

Edited May 31, 2010 by Loren
corrected image

[Reborn996]

Loren, this does not look like the intake distributor for a 2004 Cayenne Turbo 4.5 liter...its missing a few runners. ;)

Also, since this code is for a leak before the throttle body could it still be the intake distributor after it?

[Loren]

:oops: yeah, sorry grabbed the wrong image. I have corrected it now.

[Reborn996]

Thanks Loren! I have not messed with the intake distributor in any way so it would be odd to have a leak there... also, I do notice I can get full boost of .8+ with my EVO tune, but for some reason I still get the code. Even though it says the leak is before the throttle body do you still think it could be the intake distributor? Could any sensor (other than the boost pressure which I already replaced) cause this DTC? Thanks

P.S. The Throttle valve listed in the description for my DTC is the part #10 in the diagram above right?

Edited June 1, 2010 by Reborn996

[Loren]

This is everything in OBD II manual for P2281

[Reborn996]

Okay, you will not believe this one.... first, I have to say I finally found the leak after months of guessing and the dealer not finding it on multiple visits. Second, I hate to say it Loren but you were wrong on the intake distributor... it is actually part # 955-110-046-00 and is the Y-pipe in front of the throttle body according to my PET catalog listing. Now here is the funny/scary part, the diagnosis/troubleshooting says to check the intake distributor for leaks... so....

Intake Distributor

I bought the Porsche test tool mentioned above (I won't mention how much I had to pay!) and went to Sears and bought a compressor with built in regulator. It took me about an hour to hook everything up but on the first shot of pressurizing the system I found the leak... drum roll please...

IT WAS THE **** INTAKE DISTRIBUTOR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Now why Porsche could not determine this when it is mentioned in the service manual is beyond me. What is even more interesting is that after replacing all the o-rings and one of the boost pipes and finding nothing else visually wrong it was the boost test that finally showed it. Believe it or not but it was the seam where the two plastic halves that make up the intake distributor in the front part where the V section is that was leaking. No way to see it visually, but boy could you feel the air pouring out of the seam when you pressurized the system.

So, after months of BS and untold money I am now 99% sure I will have a properly running Cayenne next week once the new intake distributor comes in. I will admit, this is a very good example of where the all metal IPD plenum would come in handy! :)

P.S. According to the website above the part I needed runs about $33! Go figure.... LOL

Edited June 10, 2010 by Reborn996

[PTEC]

Nice work. Those tools are about the only way to diagnose a boost leak unless something is completely loose.

[mbagge01]

I just ordered the pressure testing setup listed above to see if I have a boost leak. I am assuming that I remove the MAF's and connect the two sealing caps to the plastic pipes that go to the turbo on each side? Up to what pressure can I put through the system to check for a leak. I have EVOM diverter valves and wondering what PSI is safe to check for leaks what PSI should normally be held in the system. Thanks.

[bigbuzuki]

Set compressed-air reducer to 0.2 bar (max 1.2 bar absolute pressure).

Here is a diagram of the leak test kit installed.

Arrow points to possible leak location.

Edited December 16, 2012 by bigbuzuki

[mbagge01]

Do I need to take the oil cap off when testing to decompress the pcv system.

[mbagge01]

Does anyone happen to have the TSB for checking boost leaks with the porsche caps testers. I looked through the TSB on this site and could not find anything. Thanks