# B7 A4 2.0T Gas Cap Message and CEL afterwards



## AlbGuy40 (Jun 23, 2005)

Hi guys,

2 days after driving my 2008 A4 I got a random Gas Cap error message in the instrument cluster... I pulled over and as I suspected the gas cap was on tight since I had just filled up the night before and made sure to get atleast 2-3 clicks from the cap...

I didn't think much of it and went to work with the message still on. At lunch time I was showing the car to a few friends and we went to grab a bite to eat... As expected the message was no longer there but less than 2 minutes after turning the car on I got the dreaded CEL (which I had in my GTI for 2+ years)... 

When I went to get the language changed on the car to someone with vagcom he told me that there was a single code for "Large Evap Leak"... He cleared the code and told me not to worry about it unless it comes back...

I have been noticing some strange noises however when the CEL is not on... I hear this weird humming/droning noise (from the front) as I accelerate from a standstill up to about 10kmh but it disappears right after... This noise was NOT present when te CEL was on and the car actually ran very smoothly and didn't seem to have lost any power whatsoever...

I have a 2 year comprehensive extended warranty so I am not really worried, I called the wholesaler I got the car from and he told me to bring it in at any time and said hell start by just changing the fuel cap... The whole droning sound though makes me thing this is Something other than a fuel cap... Do you guys have any ideas? 

I am 100% sure the noise is correlated with the CEL and have a strong feeling that once again as soon as the CEL comes on the noise will be gonne...


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## AlbGuy40 (Jun 23, 2005)

So the gas cap error message came on again 2 nights ago but went off on its own a few minutes later... I checked the actual cap a few minutes later and lubed the rubber o ring since it seemed to be super hard... I also ended up cleaning the cap and putting a decent amount of force when I put it back on... I haven't heard the strange humming noise ever since and it has been almost 200km (10 on/off cycles) with no Gas cap message and no CEL... Keeping my fingers crossed that maybe it had something to do with the cap not creating a perfect seal...


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## AlbGuy40 (Jun 23, 2005)

On my way back home tonight the light came back on... Off to replace the gas cap and see if that will fix anything... It looks like I'll definitely be needing a Vagcom tool for this car...


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## najel (Apr 10, 2008)

On my Passat I got the same message the other day. However my code was Small EVAP leak. I know that until 2007 or so VW used a gas cap that had a bad seal, and mine is still that old part no. Don't know about Audi though. I would think though that if it says large EVAP leak if it't the seal in your gas cap you shpuld almost be able to see that something is wrong.
Anyway sounds like your wholesaler is willing to help you out so that is good, finding an EVAP leak can be pretty tricky and take some time. good luck!
Oh and the noise I think might be the EVAP leak detection pump?


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## AlbGuy40 (Jun 23, 2005)

The weird sound that I was hearing the first couple
Of days of owning the car is gonne and I haven't heard it in almost 1 week now... As for the check engine light it is still there... Getting a new gas cap tomorrow so I will see if it comes back after it gets reset


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## AlbGuy40 (Jun 23, 2005)

So I got a new gas cap for free but that didn't look like it solved the problem because the gas cap message came on the next day... And from the looks of it I am gonna be getting the CEL anytime now... Time to order a CAN reader and start diagnosing myself...


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## obdboost (Feb 27, 2010)

what have you check besides the gas cap? check the n80 valve, it quick and easy. if you have a vag com you can test the ldp


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## AlbGuy40 (Jun 23, 2005)

obdboost said:


> what have you check besides the gas cap? check the n80 valve, it quick and easy. if you have a vag com you can test the ldp


I just ordered a V Checker Pro and should be getting it in a couple weeks so I can't really check readiness right now... I visually checked the rubber hoses on both sides of the n80 valve but haven't pulled the actual valve out since it still has the original crimp connectors... Both rubber hoses however feel sturdy and they don't have any cuts anywhere... Also followed the line to the next rubber section by the air box and that too doesnt have any signs of damage... 

Does anyone have a diagram of the whole evap system by any chance? From my understanding that line seems to be going down the passenger wheel well and all the way to the back (haven't checked that section out yet)...

I just noticed something strange with the actual inlet of the fuel tank... When I take the cap off I see a metal wire sticking out of the side of the opening... I am going to take a picture so that you can see it better

Here is the wire I am talking about... It's on the left side...


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## obdboost (Feb 27, 2010)

n80 valves fail, best way to check them is with a vaccum pump, and tap the valve on paper to check for carbon. what do u need for a diagram? i maybe able to help


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## AlbGuy40 (Jun 23, 2005)

I was thinking of a diagram showing all the hose routings for the EVAP system... Is that wire sticking out of my inlet for the tank normal though? Does anyone else have it?


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## AlbGuy40 (Jun 23, 2005)

Something strange is happening also... The two times that I have gotten the CEL cleared the car has run very very strong and pulling hard in 2nd through 5th... However after the CEL comes on I can feel that it's definitely running a little slower... From what I can remember on my 1.8T though it doesn't feel like limp mode, only feels like its not holding boost/ not boosting high enough... I'm counting down the days till I get the reader so I can start measuring some blocks...


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## AlbGuy40 (Jun 23, 2005)

So today I got my V Checker Pro and hooked it up right away to see what code exactly I have however even though I have a CEL on, I was amazed when the reader told
Me "No Fault Codes Found" under the engine menu... I tried numerous times and I got the same results... When I actually erased the "invincible code", the CEL disappeared... Am I missing something here?


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## shadowinfector (Jun 12, 2007)

hello, i know this is an old thread but i am having the same exact issue......to the op - the vhecker pro was not able to scan mine either, but i have a real ross tech vag com which i scanned and i got a code of 001109 - EVAP System: Large Leak Detected, just fyi.......i changed the gas cap and n80. still same code recurring....just wondering if you ever got this fixed...thanks for the reply


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