CEL - P0456 - EVAP Small Leak troubleshooting *SOLVED*

[kpatz]

I've had the car for one year and 2 days and got my first CEL yesterday.

When I sicked my VAG-COM on it, I got this code:

16840 - EVAP System: Very Small Leak Detected
P0456 - 002 - Lower Limit Exceeded - MIL On

I had this code last fall (intermittent, no CEL) and reseating the hoses on the purge valve behind the airbox solved the problem. No such luck this time.

I leak tested using block 71 in Basic Settings. I removed and replaced the gas cap. I jiggled the hoses on the purge valve again. So far the leak tests have all come up Small Leak, except when I disconnected the left-hand hose from the purge valve and plugged it.

Here's the purge valve:



Here's the hose I disconnected and plugged, which resulted in NO leak detected:



And a diagram out of the Bentley manual:



What I'm wondering is, if disconnecting the purge valve and plugging the line stopped the leak, does that mean my purge valve is bad?

I'm going to buy some reusable hose clamps today, and do some more troubleshooting. So far that one connection was the only one I could remove easily last night without destroying the one-use clamp.

[quattrotman]

No idea...but most of the time that code comes up, from what the dealer told me, it's the gas cap.They said like 95% of the time that's all it is.

[kpatz]

The gas cap was the first thing I checked. I removed it and retightened it more than once.

The fact that the leak test passes if I cap off the aforementioned hose going from the canister to the purge valve, leads me to believe it isn't the gas cap.

[quattrotman]

Interesting. Well, I've only had it come up once but if it continues, I'll keep your suggestion in mind.

[kpatz]

I picked up a purge valve at the local VW dealer on the way home from work, put it in, cleared codes and ran a leak test, and bingo, no more leak!

Hopefully I won't see that CEL again for a long time...

[KnivesOut]

I knocked that hose off by accident when I was mandhandling my air filter out a couple weeks ago. Slipped it back on and have had no problems since. Did not know that belonged to the purge valve.

[ehfour]

I picked up a purge valve at the local VW dealer on the way home from work, put it in, cleared codes and ran a leak test, and bingo, no more leak!

Hopefully I won't see that CEL again for a long time...

Kind of an old thread

But

Do you have the part # for the check valve?

[aLeXliu911]

Do you have the part # for the check valve?

x2....i have that issue too.

[1/4 scale]

I just changed mine due to a similar problem.

[kpatz]

I don't have the part number handy, I would have to dig up the receipt, which is at home and I'm at work. But the dealership can look it up for you, or get the number off the valve that's in your car now.

AFAIK, the part may be different depending on model year/VIN range.

Another tip, make sure the hoses are on good and tight. The EVAP system is very sensitive to small leaks, I had my P0456 code come back a couple times after messing around the airbox. Reseating everything and tightening down the clamps (I use the screw type clamps) solved the problem.

[ehfour]

I don't have the part number handy, I would have to dig up the receipt, which is at home and I'm at work. But the dealership can look it up for you, or get the number off the valve that's in your car now.

AFAIK, the part may be different depending on model year/VIN range.

Another tip, make sure the hoses are on good and tight. The EVAP system is very sensitive to small leaks, I had my P0456 code come back a couple times after messing around the airbox. Reseating everything and tightening down the clamps (I use the screw type clamps) solved the problem.

Good to know!

Thanks

[1/4 scale]

Do you have the part # for the check valve?

x2....i have that issue too.

1C0-906-517-A
but this may vary per VIN no.

[swizzchard]

does it actually cause problems if we have a 'small' leak there?

[1/4 scale]

you may throw a code

[Tone-Dogg]

great thread, thank you, I'm throwing the same code right now. Will look into. Again Thanks for the pix

[plug1]

great thread, thank you, I'm throwing the same code right now. Will look into. Again Thanks for the pix

Same here, I just cleared this very code not more than 20 mins ago before heading in to work. I was happy to see this thread at the top of the forum this morning...perfect.

[Tone-Dogg]

Same here, I just cleared this very code not more than 20 mins ago before heading in to work. I was happy to see this thread at the top of the forum this morning...perfect.

Must be Very common, good luck

[rbj325]

Must be Very common, good luck

Yeah bonus points. I'm fighting with my car and this code right now as well.

[[email protected]]

Wow, sounds like lots of people have this code...not to rub it in or anything, but I don't!

If there is a small leak or the check valve is bad, the purge valve will receive a boost signal...which isn't good. When there's a small leak the motor will try and compensate, so you may see raised RPM's or leaned out fuel trim.

Either way, a small leak does affect the car...not a whole lot, but it does. As the leak gets worse, the motor's compensation for it will become more and more pronounced.

Hope that helps!

[headshok2002]

Bringing this back...

What kind of symptoms would we see here? My girlfriend's 02 A4 has a CEL and is throwing this code. It's been intermittent for several months now but yesterday she said the car 'felt different' when accelerating. Kind of like she gave it gas, and it didn't want to go. Yesterday was very hot, too, so it might have been a heat-soak issue, too.

[Tone-Dogg]

Bringing this back...

What kind of symptoms would we see here? My girlfriend's 02 A4 has a CEL and is throwing this code. It's been intermittent for several months now but yesterday she said the car 'felt different' when accelerating. Kind of like she gave it gas, and it didn't want to go. Yesterday was very hot, too, so it might have been a heat-soak issue, too.

I really didn't see any sympotoms, I just got a CEL, I'm kind of a dork when it comes to Vag com too. I kind of scan my cars a lot to see whats going on. For me it turned out to be the gas cap when I first posted in this thread. Sorry I coundn't be more help.

[rx7cblink]

I just got a CEL p0456 i tighten gas cap and checked but still have code. any more info on this thanks..

[tonio757]

Just to share my experience:

When I bought the car (A4 b6 1.8tqm) I had:
- the MIL on
- EVAP code Lower limit exceeded
- Not able to fill up more than 3 liters wihtout letting vacuum out
- vaccuum in the Tank.


What I did was:

- change the canister
=> I was able to fill up again, it was clogged. but the MIL was still on. (small leak/lower limit exceeded)

- change the N80 purge valve
=> MIL still on! although the old N80 was full debris from canister

- change the check valve just next to the n80
=> MIL still on, lower limit exceeded

- change another check valve - number 50 on this thread:
This thread

=>No more MIL!! Everything back to normal....

I am in the process of replacing all other check valves now.

Good luck!

[Ac3]

bringing this back yet again. i have this code as well, i have an 02 a4 1.8t 5 spd quattro. not the gas cap and i did replace the n80 valve above the airbox with one from a b7, cleared the code and still came back. where else should i look guys? no vagcom.

[Jborch8]

bringing this back yet again. i have this code as well, i have an 02 a4 1.8t 5 spd quattro. not the gas cap and i did replace the n80 valve above the airbox with one from a b7, cleared the code and still came back. where else should i look guys? no vagcom.

Not entirely sure, but I did read a lot regarding this issue. There's a thread somewhere here discussing the evap canister being replaced. May want to check there.

[SVtracker]

Going to reopen this thread from the dead.

I have a 2014 Audi A4 2.0L with 14000 miles on it.
I installed the APR stage 1 two months ago and the Eurocode FMIC three weeks ago.

I didnt start using my vag.com tool until after installing the FMIC. Once per week for the last three weeks, I would get the P0456: evap very small leak code. I would run the auto scan and get this code (I didnt not run "select control module" function block testing). No check engine light on the dash board....just a soft code per the auto scan.
Then yesterday, the check engine light showed up on the dashboard. Autoscan says P0456, and I cleared it.

Yes, I made sure the gas cap was closed and retightened/clicked. Still throws the code after clearing the code with the vag.com tool and tightening.


Called APR and Ecodetuning and they say it is due to my EVAP system and the persons I talked to say that they have never heard of this issue from customers.

Going to run the vag.com tool to see if it is my charcoal canister or purge valve. Post #23 in this thread mentioned a check valve (but I dont know if my A4 B8 chassis uses a check valve).
I dont know how to use the block testing on the scan tool and need to read up on it. Any constructive pointers/hints are welcome. It may be my purge valve, but I don't want to spend money on it yet until I confirm the valve is the problem.

[Scolex]

I just got my '10 A5 2.0T back from the Audi dealer with the P0456 code. For my vehicle, I need the purge valve (06H-133-781-CK), which is an assembly of the valve and hoses. Part Number 06H906517B is quite similar, but for only the valve, and associated with a different engine size, YMMV. This part is used by the 1.8T and the 5.2T engines (TT and R8), so its a big difference. A4s and A5s have different assemblies apparantly.

[gtsingh91]

Bringing this back from the dead, again. I used to get this code intermittently and it would turn itself off. The day i was going to get NYS Inspection, the CEL came on and it was P0456. I checked my gas gap and retightened it, but it came back on exactly 25.0 miles later. I'm going to check the purge valve to see if that fixes it.