CEL P0451 Code

[The Machine]

Does anyone have any experience with this code on their B8/B8.5? My CEL came on about 2 weeks ago with this code when I started the car one morning and I just cleared it figuring maybe it was a fluke. Two days ago I went to get gas and for the first time the car had a hard time filling up. The pump would click off no matter how the attendant adjusted the nozzle and even when trying to pump the gas by just holding the handle down instead of putting it on an autofill position. Today when I left the gym and started the car, the CEL came back on again for the same P0451 code, so now I'm guessing it may not be a fluke and something needs to be addressed in the EVAP system.

Any thoughts or suggestions would be great, thanks!

In case this matters, mods are:
CTS Turbo Intake
AWE Tuning Touring Exhaust (stock DP's)
APR Stage 1 tune

[The Machine]

I found this DIY on the B8 A4 side. http://www.audizine.com/forum/showthread.php/749780-DIY-Charcoal-Canister-Leak-Detection-Pump-Evap-CEL-Codes-P0445-Gas-pump-issue

Although he was getting a different CEL code, he was having the same fuel cutoff like I was experiencing the other day. Can anyone confirm that the carbon canister is in the same location on the S4 as it is on the A4? Also anything else I should maybe look into first before jumping right into buying a $200+ part to throw at it to see if that fixes the issue?

[The Machine]

It was tough to keep up with all the responses, but in case anyone ever comes across this again, the fix the was the charcoal canister. CEL is gone and the car was able to fill up with gas normally again.

https://farm5.staticflickr.com/4638/38503023165_b4f82528bd_c.jpg (https://flic.kr/p/21Eo4mZ)Untitled (https://flic.kr/p/21Eo4mZ) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

https://farm5.staticflickr.com/4733/38503023265_6a1f633620_c.jpg (https://flic.kr/p/21Eo4oH)Untitled (https://flic.kr/p/21Eo4oH) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

[The Machine]

Sorry to bump this up, but I wanted to add one last update. The P0451 CEL came back on a week or so later. Since the code reads "Evap Emission System Pressure Sensor Performance", I was able to find out that this sensor is actually integrated into the leak detection pump that is attached to the side of the charcoal canister. So needless to say, I had to remove the charcoal canister again and I installed a new leak detection pump. I've been driving the car around for the last 3 weeks after installing the new pump and the CEL has not come back on.

https://farm5.staticflickr.com/4603/39772147122_4cf8ef9e45_c.jpg (https://flic.kr/p/23AwDGw)Untitled (https://flic.kr/p/23AwDGw) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

https://farm5.staticflickr.com/4716/28025464289_e1770b2eed_c.jpg (https://flic.kr/p/JGvQ9a)Untitled (https://flic.kr/p/JGvQ9a) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

[davesxx01]

Thanks for the update!

[saxon]

thanks for the updates, i am sure this post will help someone in the future

[The Machine]

No problem guys, I hate coming across threads that people start and then they never post a final outcome once their car is fixed. I really don't want to be "that guy" when someone could have the same issue in the future.

[Rodizzle]

Good Info [emoji1417] thanks for the update


Sent from my iPhone using Tapatalk

[The Machine]

So I figured I would add to this thread since this is relates and maybe an additional thing to check incase you should ever get this code.

So about 3 weeks past since I installed the new canister and LDP and I went to fill up with gas and had the same issue with the pump cutting off. Shortly there after the P0451 code came back. Figuring I was missing something I decided to just take it to the Audi dealer for diagnosis. I went to Cherry Hill Audi and they were actually awesome to deal with. The service advisor even texted me pictures of what was going on which I have never seen before from a dealership, so I was super happy with that.

Anyway, the problem was that the charcoal canister I recently bought was filling up with water and was causing my fillup/CEL issue. So how did this happen you might ask? Well back when I bought my car through a private sale, it was REALLY low to the ground. Apparently the previous owner cut a section of the fender liner out, I guess due to rubbing, and it was exposing the vapor canister filter at the top of the wheel well. When driving in the rain or through a puddle, as water gets thrown up by the tire, it was going into this filter and running down the tube attached to it and into the charcoal canister. Talk about dumb luck. So I bought a new charcoal canister, a vapor canister filter, and a used fender liner to install to keep the pump sealed off from the elements. So far after the first fillup and 100 miles or so there have been no issues.


Removed charcoal canister and vapor canister filter with water on the bench from coming out of the charcoal canister

https://farm5.staticflickr.com/4743/38863139170_68118d2077_c.jpg (https://flic.kr/p/22dcKiC)Untitled (https://flic.kr/p/22dcKiC) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

Spot where the previous owner cut out a section of the fender liner

https://farm5.staticflickr.com/4653/26802160518_73e818185d_c.jpg (https://flic.kr/p/GQq5xQ)Untitled (https://flic.kr/p/GQq5xQ) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

New vapor canister filter installed

https://farm5.staticflickr.com/4744/25802584747_115a734a6a_c.jpg (https://flic.kr/p/Fj5ZuP)Untitled (https://flic.kr/p/Fj5ZuP) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr

https://farm5.staticflickr.com/4784/40673423621_69e9b34263_c.jpg (https://flic.kr/p/24YaVNv)Untitled (https://flic.kr/p/24YaVNv) by gccgoalie33 (https://www.flickr.com/photos/124710444@N06/), on Flickr