GTI with a P0456 CEL DTC Code

So, my 2008 GTI (FSI BPY) has been throwing gas cap MIL warning for a few months now, but they were only intermittent. The gas cap MIL is no more, but now I have the constant presence of an illuminated yellow engine in my speedo, and after a quick scan I found out that CEL is a P0456 (EVAP small leak detected) DTC.

I was reading through some other P0456 threads, but I noticed most mentioned a code, but the OP never seemed to follow up -- so there weren't any conclusions like, "hey, just installed part XYZ and it solved the P0456." To be sure, there was a lot of speculating, just very little verification.

The above said, I just ordered an OEM Bosch Purge Valve (only $14.70 btw) and was wondering if anyone else here was able to clear a P0456 with a new Purge Valve? As an aside, I realized after reading other threads that I may kill two birds with one stone and ordered an INA brand cam follower as well (only $18.86 vs dealer's $68).

Thanks.

I have TSI engine and had the same problem and same code. Since my purge value is significantly more expensive I went the cheap route first and purchased a new gas cap from the dealer. Installed it in the lot, turned on ignition and no more CEL....didn't even have to clear it. Might want to start there and see where that get's you.......

Nitrorea said:

I have TSI engine and had the same problem and same code. Since my purge value is significantly more expensive I went the cheap route first and purchased a new gas cap from the dealer. Installed it in the lot, turned on ignition and no more CEL....didn't even have to clear it. Might want to start there and see where that get's you.......

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Thanks, I was of course suspicious of the gas cap, but have read about issues with the purge valve and the purge valve is cheaper than the damn gas cap. An OEM gas cap is over $30 shipped and I'm not sure what the dealer charges.

Do you or anyone else happen to know what exactly fails in the gas cap? I would imagine that a gas cap (esp a $30 one) could be repaired unless something broke.

Mine never said it needed a cap, it just said to replace the n80 so I did. and $30 isnt bad for a cap considering junk aftermarket ones are like $15. usually its the seal that goes tho

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The n80 was the prime suspect in these cases, something cheap you can try is to put some light lube on the gas cap seal and see if it seals any better, provided that is the culprit

707Stang said:

The n80 was the prime suspect in these cases, something cheap you can try is to put some light lube on the gas cap seal and see if it seals any better, provided that is the culprit

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Well, I changed the purge valve this weekend and still have the CEL lit up on my dash. Btw, as an aside, those banjo clips are a pain in the arse. I couldn't cut them off with good wire cutting pliers, so I pulled out these 16" Harbor Freight nippers and those babies did the trick.

Anywho, thanks for the lube on the O ring idea. Honestly, I'll often just replace a suspect part if it's cheap enough, but given the gas cap sells for around $35 ($46 at dealer) and even the O ring itself to repair the gas cap is a $15 dealer part... I'm not as quick to buy either of them. I think I will just use my scanner to clear the DTC code, and - now that purge valve is changed - see if it comes up again. If it does, then I guess it makes sense to address the gas cap, next.

Joshohol said:

Mine never said it needed a cap, it just said to replace the n80 so I did. and $30 isnt bad for a cap considering junk aftermarket ones are like $15. usually its the seal that goes tho

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Thanks. The gas cap O ring (seal) is a tricky part to track down online, but found them fairly cheap... it's just the shipping that's been ridiculous. I changed my purge valve and still have the CEL, so if that remains the case, then I'll figure out whether to repair the gas cap with the O ring or just bite the bullet and buy a whole new (overpriced) gas cap.

Well, just erased the DTC code the other day (after changing the purge valve, since the DTC code didn't go away on it's own). So far, so good... there hasn't been a CEL or gas cap MIL since I changed the purge valve and erased the code. On top of that, the car is definitely running smoother than it was the last few months.

I'll update this thread if I get another CEL or gas cap MIL... but the good news is that I'm still using the same old gas cap that's been on the car since 2008 and only changed the purge valve (and erased the DTC) and so far so good.

MagicMK said:

Well, just erased the DTC code the other day (after changing the purge valve, since the DTC code didn't go away on it's own). So far, so good... there hasn't been a CEL or gas cap MIL since I changed the purge valve and erased the code. On top of that, the car is definitely running smoother than it was the last few months.

I'll update this thread if I get another CEL or gas cap MIL... but the good news is that I'm still using the same old gas cap that's been on the car since 2008 and only changed the purge valve (and erased the DTC) and so far so good.

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Just go to the wreckers to get a used gas cap. Inexpensive way to troubleshoot if your code comes back up.

Morrow said:

Just go to the wreckers to get a used gas cap. Inexpensive way to troubleshoot if your code comes back up.

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Everything has been fine, that's the point... so, no need to even bother with the gas cap. I think my original gas cap MIL warnings were really the Purge valve malfunctioning and triggering a small leak in the EVAP and the computer read that as a possible loose gas cap issue.

I looked at the gas cap and (for the first time) looked at the high quality gasket VW uses for the gas cap and it struck me as odd that the gas cap would even fail given the apparently quality. At any rate, I'm not getting any DTC codes or gas cap MILs at this point, so even though I found a new cap for $32 shipped, I'd rather keep the $32 in my pocket.

Awesome thread. Just got p0456 code. On the way to work the other day my gas cap MIL turned on. So I tightened it down and that was it. The following day the same thing. Then full solid CEL came on. Good to know that there is not much effort involved. I can swap n80 and hopefully this will take care of CEL. I saw some gas cap gaskets for like $8 on ebay, so this will be next step.

svarasnj said:

Awesome thread. Just got p0456 code. On the way to work the other day my gas cap MIL turned on. So I tightened it down and that was it. The following day the same thing. Then full solid CEL came on. Good to know that there is not much effort involved. I can swap n80 and hopefully this will take care of CEL. I saw some gas cap gaskets for like $8 on ebay, so this will be next step.

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Just as a reminder, my issue was the purge valve and the Check Engine did not go off even after I replaced it. The car was clearly running better, though (smoother), so I just erased the code with my scanner and it hasn't come on since.

The above said, I'm thinking that many of the gas cap replacements are likely unnecessary... it seems to me that the purge valve is a much more likely culprit than the gas cap. As an aside, I did "top off" my gas tank on a few occasions before I received the MIL and CEL. So, doubtful that the cap is an issue, and the purge valve is both inexpensive and easy to change, but make sure you erase your DTC after you make the change because it doesn't appear that even when the issue is fixed that the VW computer turns off the CEL.

Good luck.