Evap error codes-what do they mean, where to look?

A6 All/ S6 All
#1

Got some evap error codes yesterday morning. Solid CEL. Here’s the log:

3 Faults Found:

001110 - EVAP System
P0456 - 001 - Very Small Leak Detected - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 165268 km
Time Indication: 0
Date: 2017.07.22
Time: 09:30:03

         Freeze Frame:
                RPM: 2351 /min
                Load: 27.4 %
                Speed: 108.0 km/h
                Temperature: 79.0∞C
                Temperature: 24.0∞C
                Absolute Pres.: 980.0 mbar
                Voltage: 13.970 V

001109 - EVAP System
P0455 - 001 - Large Leak Detected - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 165871 km
Time Indication: 0
Date: 2017.07.23
Time: 09:07:30

         Freeze Frame:
                RPM: 767 /min
                Load: 25.1 %
                Speed: 12.0 km/h
                Temperature: 93.0∞C
                Temperature: 25.0∞C
                Absolute Pres.: 980.0 mbar
                Voltage: 13.970 V

001090 - EVAP Emission Control Sys
P0442 - 001 - Small Leak - MIL ON
Freeze Frame:
Fault Status: 11100001
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 166205 km
Time Indication: 0
Date: 2017.07.24
Time: 07:50:48

         Freeze Frame:
                RPM: 644 /min
                Load: 26.7 %
                Speed: 0.0 km/h
                Temperature: 67.0∞C
                Temperature: 23.0∞C
                Absolute Pres.: 970.0 mbar
                Voltage: 13.843 V

Where should I look to solve this? Thanks again for the help, guys.

#2

Looks to be gas cap related as per ross tech website.

#3

I went and check the cap. Rotated it a bunch of times so in clicked.
Cleared the codes. Started it and it didn’t come on. We’ll see… That would be something if that’s all it was (and I’d be extremely grateful).

#4

16840/P0456/001110 - EVAP System: Very Small Leak Detected
Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Fuel Cap not fully attached
Evaporative Emission (EVAP) System leaking/faulty
Possible Solutions
Check Fuel Cap
Check Evaporative Emission (EVAP) System

16839/P0455/001109 - EVAP System: Large Leak Detected
Possible Causes
Gas Cap loose/missing
EVAP System Leaking
Possible Solutions
Check Gas Cap
Check EVAP System
Check to make sure EVAP purge valve is not installed backwards

16826/P0442/001090 - EVAP Emission Control Sys: Small Leak
Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Evaporative Emission (EVAP) System leaking
Possible Solutions
Check Evaporative Emission (EVAP) System Sealing
Check Fuel Cap

#5

It can be a buntch of things. gas cap is the standard easy leak. But on a higher mile car you can see your evap solenoid sticking. Usually you don’t get a evap check until the car has been running for a little while so check in the next few days. if it comes back you can always dig deeper. But gas cap would be a nice easy fix. I have had it be just that on my car before…

#6

The evap purge valve is probably sticking.

This is what I would do to test it.

  1. Get a flat style locking vice grips.
  2. Go drive the car until it is warmed up to the middle of the gauge/at least 80°C for coolant temp and then go to a safe spot to have the car parked/standing with the engine running.
  3. Pop the hood and locate the evap purge valve. I think that it is towards the back of the engine by the throttle bodies.
  4. Clamp the rubber section of the line after the evap purge valve closed with the locking vice grips.
  5. Have the engine running at idle, hook up the vagcom, clear the engine codes in both 01 and 11 engine electronics.
  6. Go into the basic settings portion of the 01 engine electronics, go to channel 71, click the test on option towards the top right of the screen, and wait for a result to appear in the fourth measuring value block. Should be like an abrievated System Passed or System Not Passed.
  7. If the test doesn’t work in 01 engine electronics then try 11 engine electronics.
  8. Most likely the system will pass with the evap line after the purge valve clamped off because you have eliminated the leak from the purge valve. Just to be sure repeat steps 5-7 with the line not clamped off and it will probably fail again.

Should be pretty easy to replace the purge valve since it is right on top of the engine. I still remember the majority of the testing channels for the old Bosch style readiness codes but they have been changed on the newer Siemens ECUs.

#7

Thank you very much! I will check this weekend and report back.

#8

CEL came on after about 10-15 of driving this morning. Will check the codes again tonight, and do the test JimmyBones recommends above tomorrow.

#9

BTW, is there a way for the gas cap to fail?

#10

Not surprising. The ECUs run the test that I described at idle after the engine is warmed up and it takes like two minutes for the test to run. That is one of the most important emissions systems on the car other than oxygen sensors and catalytic converters since leaking fuel is a major fire and health hazard along with it hurts the environment.

Yes but you would need a smoke machine with the correct adapter fitting for the gas cap. I have personally never seen a tight gas cap cause an evap leak but I guess it is possible that the seal could have been damaged. Would be easy enough to check by just removing the cap and taking a look at the seal. The only reason that I have ever replaced a gas cap was for the stupid sensor that shows up on the dash to tell you that the gas cap is not on with the older cars or if the gas station in New Jersey put the wrong cap from another Audi on since you can’t pump your own gas in that stupid state or Oregon.

#11

When I go to basic settings in either 1-engine or 11-engine, there is no test button In the upper right corner for channel 071. The four boxes say Reed Closed, Abort, , Test Off. Text in the center of the screen says Basic Settings: Off.

I clicked On/Off/Next and now the rightmost box says Test On and the left most box says Reed Open, but very briefly will switch to Reed Closed.

Now boxes read Reed Closed, Large Leak, , System Not OK.

So I have to block the hose like you said. Which side? Can’t tell by looking.

#12

I tried blocking each of the hoses separately. It still says System Not OK and Large Leak.

Assuming I did it right, thoughts on what to try next?

#13

So I pulled the hoses off the solenoid valve. The one off the side came off easily. The one on the end was hard to get off. You could hear the vacuum release once I removed the hose. If air is supposed to be pulled through that valve. Maybe it’s stuck closed?

And I can’t believe how hot everything get under the hood. It surprises me every time.

#14

If I understand correctly… yes, air should be getting sucked in to the short hose that comes off of the evap valve and into the top of the intake once you take that hose off of the evap valve. Air should not be sucked in the other way that eventually leads back to the fuel tank.

What is probably happening is it is stuck open or only stuck open for a short period of time when it’s supposed to be closed.

You can take the valve out and apply 12v to it while you try to blow through it. When you apply 12v, you should be able to blow through it. Once you stop supplying it with 12v, then you should not be able to blow through it. You might have to try this many (many!) times in order to replicate an intermittent sticking evap purge valve.

#15

Thanks for the additional advice. I’ll have a vacuum gauge tomorrow. I’ll put a vacuum on and keep cycling it by applying voltage.

It makes sense that something is intermittently stuck open because I can clear the codes and then drive around for some time without anything happening, including turning the car on and off between trips, with no CEL.

#16

In case anyone is interested… Here’s a good 5 minute video describing everything about the N80’s common issues:

https://www.youtube.com/watch?v=vTXdpo02qfU

#17

Thanks for the post.

Based on that video, I think I’ll just replace it anyway and be done with it. Sounds like a component with a finite lifespan that will fail eventually anyway. $44 on FCP and I need some other things.

I will test once I replace though.

#18

Alright, now I’m confused again. ::slight_smile:

It looks like there’s two valves that are at least somewhat similar in the evap system.

Solenoid valve: https://www.ecstuning.com/b-pierburg-parts/solenoid-valve-priced-each/037906283c~pie/

Purge valve: https://www.ecstuning.com/b-bosch-parts/purge-valve/06e906517a~bos/

The purge valve is the one shown in the YouTube video. The Solenoid valve is the one I’ve been clamping the hoses on, and it is located on the front of the intake manifold on the driver’s side. I found it by doing a keyword search in Bentley and looking at a diagram. Have I been checking out the wrong one? If so, where is the other one exactly?

#19

The purge valve is the one that you needed to clamp the hoses for. The solenoid valves rarely ever go bad.

#20

It is located in the middle of the engine bay back by the firewall. You should see a mesh-covered hose coming in to the left side of the purge valve (If you’re standing in front of the car looking in to the engine bay) and a short rubber hose coming from the right side of the purge valve leading into the upper intake.