bobo83

I just completed the thermostat replacement on my 957 08 Cayenne S and everything went well. Except now, i get a the code 0455 - Evaporative emission system leak detected (Large leak) No signal/communication. Did I miss connecting a line or is it related to the gas cap? Anyone know?

RajDatta

Did you ever figure out. I did the exact same service and got the same code. My wife did get gas recently and some of the answers point to a loose gas cap. The other option is to remove the valve covers and possibly the intake to check if everything is connected correctly.
Please let me know if you figured this out.

bobo83

I still had the error code up till last night. I removed the intake manifold completely to see if anything was missed. I did notice that on the left bank (drivers side) that there was some oil/gas residue on one of the ports. I have a feeling that the intake manifold was not sitting correct or flush. I'll drive the Cayenne around today and see if it went away.

968TurboS - did you ever figure yours out? Was it just the gas cap?

RajDatta

I asked my wife and she did not get any gas so it can't be that. I did perform the same removal of intake manifold to do the thermostat job, so I am certain I need to have a 2nd look at all the connections.
I plan to take it apart today and will report back.

bobo83

So far so good today after reinstalling the intake manifold. I'll give it some more time before I know.

RajDatta

It was the vacuum fittings on the back of the manifold. The 90degree connectors were loose and the lines get sliding out. I used a new set of connectors and so far no more CEL.

bobo83

That is awesome news! I drove it the Cayenne around the other day and so far so good. Do you have a part number for the 90 degree connectors?

bobo83

I'm still having issues with this. I reconnected all the hoses and this is what I've been thinking so far.

1) I found oil in my intake manifold, so I'm assuming that possibly my AoS is going and this could cause P0455?
2) the line vacuum one at the back of the engine is cracked and I can't see it, so I might just replace it.
3) the oil residue that I find around the intake manifold could be caused by old or worn gaskets which need to be replaced.

Any ideas would be great!

bobo83

Ok, so I figured this out. The 90 degree hose at the back of the manifold kept falling off. I should have listened to 968turboS. I just replaced it and now no more error code!

kino1161

Can anyone please post pics of this 90 degree hose at the back of the manifold? The reason I ask is because after I changed my vacuum pump, I started getting this code. Could I have disturbed this 90 degree hose? Is the area I was in (replacing the vacuum pump) the same area where I could have disturbed this hose?

kino1161

No pics? Trying to get rid of my P0455 code.

thescratt

P0455 can also just mean your fuel cap is worn and not sealing properly.

EDIT - I notice this has already been suggested above. But still bears repeating. It's an intermittent fault, can just happen to come on after other things.. because Murphy's Law.. But in my experience on a 10 year old CTT it was just that, when I spent a while investigating and expecting much worse.

kino1161

Ok. I'll try to replace the gas cap and see if it returns, but it still wouldn't hurt if someone can show a pic of that 90 degree hose they are referring to.