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P0455 (evaporative emission system leak - large leak detected)

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2009 cayenne S (US spec) with 74k miles on the clock.

Check engine light on with code P0455 (evaporative emission system leak - large leak detected). Picture attached

i took it to a shop to do a smoke test, they found no external leaks. They tested the tank vent valve and leak detection pump and it failed twice. (Pic attached)


so i changed the leak detection pump (95560510702), found that the one installed was a chinese brand not oem, drove the car for two days then the light came back again! Same error code.


next step i want to change the tank vent valve (95560524101), is that the same as the purge valve? i found some DIY for an 03 -06 TT but not sure if it's the same for my 09 cayenne S. i can't find any diagram online on where the valve location is. Any help is appreciated, thanks.




WhatsApp Image 2018-08-13 at 7.13.51 PM.jpeg

WhatsApp Image 2018-08-16 at 6.47.59 PM.jpeg

WhatsApp Image 2018-08-21 at 8.22.01 PM.jpeg

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  • 3 weeks later...
On 9/7/2018 at 5:49 PM, ChuckMan said:

Having the same issue with P0455 on my 08 Cayenne S.

Do you have any info on the leak detection pump replacement? Sounds like that didn't fix the problem so have you done something else?

Hi Chuckman,


smoke test showed no leaks, so far i have changed the gas cap, leak detection pump, purge valve and CEL still came back on...

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Well I'm stumped..

Mine has now switched to showing the P0244 Code instead. I had been getting P0455 Code since having the thermostat/Waterpump/Belt/Pulley changed 2 weeks ago.

Went back to the indy who did the pump change and he stuck a computer on the OBD2 and did some tests. Since I changed the Gas cap 5 months ago, we are sure it isn't that.

Then he did some test and said he was sure it is not the purge valve (essentially he unplugged a few hoses into the purgeValve and used his own hoses and the computer to trigger the valve, which he could hear clicking and was also not able to blow air through it during the test or vice versa)..not exactly the most sound test but okay.

Then he pulled on the little 90Degree hose on the Vacumn pump behind the manifold and said it was too easy to come lose that maybe it wasn't connected. Me I couldn't tell if it was disconnected or if it came lose. 

Bottom line is, he then said it is my vacumn pump most likely the issue, then he put the little 90Deg hose back. 

After that 90Deg hose was reconnected, my code went from being P0455 to now being P0244 (go figure).

I think the P0244 code is more for the LDP being bad, but he was saying that the VacumnPump(VP) is the issue.

I also recall reading somewhere that a faulty VP will cause oil to enter the LDP, and that the LDP just needs to be cleaned and it could be ok and it's just the VP.

So I'm wondering what the heck is going on now.

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  • 1 month later...

I too had the P0455 EVAP large leak code in the summer on my 09 CTTS. I changed the gas tank cap first. It did not help. I did some more researching and ended up replacing the vacuum pump at the rear of the passenger side bank (driven by the camshaft I believe). It was leaking oil pretty bad back there. The code has not been back so far. It involves removing the intake manifold and the pump is held by 3 screws, very tight but doable. 

Hope that helps.


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  • 2 months later...

Thanks Chuckman, well P0455 is for a large leak and the P0244 is for a minor leak (like the gas cap) so i'm assuming when he put the hose back he tightened it a bit more so the leak code changed to P0244.


I have visually checked my pump for any oil leaks or signs that the seal of the pump is worn, but it looks really clean... not sure if i should undergo the process of changing it only for the light to pop up again... i've already invested more than 1000$ in what looks like a witch hunt, to the point where my wife is like leave it i don't care if it goes away or not anymore (it's my wife's car)... but you can see it still bothers me a lot everytime i jump in her car lol


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