oppositelocksmth

Hi - I've been thoroughly enjoying my 2009 GTS for the last week. Despite the mild engine tick it has been great to drive.

Going through the service records, I see the previous owner had a CEL with code P0455 for about a year - the dealership notes say "Major Air Leak Code - Advised to remove intake manifold to diagnose, customer declined."

I used my cheap OBDII reader to clear the code, and it stayed off for about 10km of city driving. I checked the vacuum pump on the back of the engine using a mity-vac on the small rubber hose, and it held vacuum. I also didn't notice any oil in the small line or the big one coming off the pump. Because of the lack of oil in the lines and the CEL staying off for about 10km of driving I'm thinking the vacuum pump is okay.
Dealership also replaced the diagnosis pump in the rear wheel well previously.

I'm wondering what are the other common culprits for the P0455 code, especially ones under the intake manifold? Is there a vacuum line and seals kit available? Is there a good write-up on step-by-step vacuum system testing?

I don't mind pulling the intake manifold and replacing all the wear items under there at once.

Thanks!
-Chris

TRINITONY

Gas tank cover or there's a T connection to rear of the intake that could get loose and trigger it. Do a search on 6speedonline.

v10rick

P0455 is not necessarily a leak, a pump with low vacuum will trigger the same fault.

To test the vacuum pump requires that you measure the vacuum while the engine is running. Using a mighty vac connected to the vacuum line to the exhaust flappers my bad pump read 10", the good pump 20", with sport mode turned off.

Before doing this pump up a vacuum with the mighty vac to confirm there is no oil pulled through the vacuum line. This happened with my pump indicating the pump seal was shot.

Libast

Pull the intake and replace all those crappy plastic vacuum lines. The ones that come off the "T" from the vacuum pump- the soft line goes out to the left and to the back to the sport exhaust, the firm lines go all over the place on the back of the engine.

Outlaw5050

I spent the last 60 days on my 09 Cayenne S with the same P0455. I will document my journey in the hopes it helps you and others.
P0455 can mean you have a large leak OR no flow at all. It's a frustrating code that can drive you crazy. Trust me.
I am just a normal guy, not a mechanic. I'm sure there are faster methods to trace down this issue, but here is all I did to fix this Check Engine Light.
I will note, my Cayenne ran just fine the entire time.
I replaced the vacuum pump off the passenger side cam (Ebay $120). Old pump was leaking oil also. The Cayenne ran better but still popped the same CEL. Atleast the oil leak was gone.
Replaced the gas cap. (Updated part $15)
I found the entire EVAP carbon canister assembly and secondary pump on Ebay for $75. Replaced all of it. It is located behind the passenger side fender liner. Same CEL.
Pressure tested the gas tank. It was good. I used the large clear vacuum pipe coming off the EVAP canister to do this, with the gas cap tight.
Cleaned up and repaired the brown ecm ground wire behind the gas fill neck rubber grommet.
Traced the vacuum line from the EVAP carbon canister to the engine bay. Blew air through it, using my air compressor. An ounce of oil shot out the vacuum hose (old vacuum pump diaphragm ruptured, causing oil into the vacuum lines) .
You haven't had the true Porsche ownership experience, until you have had oil shoot out your vacuum lines. SMH...
Spend 30 mins cleaning up the oil mess all over my inner passenger fender and brakes. Have a towel ready if you do this job!
I still had a P0455 pop after cleaning the lines but i'm glad I did it.
I replaced the AOS (Air Oil Seperator) diaphram on the top of the driver side valve cover ($49). You will find getting the top plastic cover off will be a fun all day event, filled with cursing. P0455 laughed at me and returned again.
I replaced the fuel vapor purge valve on the passenger side of the engine, near the throttle body. Porsche wanted $180 for the part. KIA uses the same Bosch part on their cars, so I ordered it for $33. My old friend P0455 returned again.
I ordered a smoke machine to find vacuum leaks, and contemplated sell this SUV. I have always worked on my own cars. No mechanic has ever touched a car of mine. I even contemplated taking it to the dealer. After a glass of moonshine and a cigar, my sanity returned.
I decided on Friday night to take off the intake manifold. Its pretty easy, about 20 hex bolts. It took 20 mins to remove.
I found the crossover valve on the back of the intake manifold was disconnected. Causing a major vacuum leak. $3 worth of vacuum hose from a local auto parts place, and I put the intake manifold back on.
My old friend P0455 is finally gone.
$295 in parts.
Still waiting on my smoke machine to arrive. I had also ordered some 12 spline hex sockets to get to the top of the fuel tank. I guess I will hold on to them in case I need to replace a fuel pump.

TRINITONY

And that's what I was referring to a my earlier post. A chap on 6speedonline had the same issue and that was the culprit.

Thanks!

leistung

I'm about to embark on this journey to fix my P0455, and I stumbled upon your post. Just wanted to say thank you first for the laugh and secondly for the information. I bought a 2008 GTS w/ 47k and have been doing maintenance myself. I've been researching this issue to be as prepared as possible and I find your post hilarious as I feel similar emotions when troubleshooting with this car. Thank you again. I know this will positively affect my experience.

googone20

Do you have to remove the intake manifold to replace this t-connection vacuum hose? I had the P0455 code pop this morning, so I am assuming this is where my issue will be. I also need to buy a new gas cap as mine is original, and the tether is broken anyway.