[loosegravel]

So after getting this 2001 1.8 turbo automatic Beetle running (finally) and driving it around for some time, I seem to have this annoying, repetitive check engine light with a PO411 code. The funny thing is, the check engine light only comes on every 500 miles or so, and only when the vehicle is fully warmed up, like on the freeway today. The secondary air pump is working momentarily as it should when the engine is cold and then it turns off after a minute or two. The inlet and pressure hoses are intact and fully seated. The O-rings are good. There are no noticeable leaks that I can see or hear. I'm confused, because I thought that the secondary air pump is only called for when the engine is cold. If that's the case, then why would it log a fault when the engine is fully warmed up?

 

[billymade]

16795/P0411/001041 - Ross-Tech Wiki

A number of possibilities; read the link above. Main thing to check; that I have seen:

1. make sure the air pump powers up and flows: good/bad?

a. any hoses broken, cracked or old: in secondary injection system?

The solenoids; listed in the link can be checked by using VCDS and turning on the output tests: good video showing this process:

VW A4: 1.8T P0411 Sec.Air Inj.Sys. Incorrect Flow Detected - YouTube

BELOW WAS A DIFFERENT CODE:

2. my problem was a "insufficient flow" code: in my case, my "kombi" valve was sticking and not working as it should: thus, the flow wasn't getting where it should have.

a. removed "kombi valve": checked with a vacuum pump tool, it did its job but it was binding and didn't have any holes (maintained vacuum). The was confusing; as the testing as per the manual: was checking that it maintained vacuum pressure. It "passed" the testing procedure but was still bad, by it binding. I replaced the part and code went away.

To get a handle on the VW SAI system: check out these two excellent how to/tech articles: they are downloadable files;

by Dan Marinucc of Motor Magazine:

http://www.motor.com/magazine/pdfs/082007_04.pdf

http://www.motor.com/magazine/pdfs/092007_04.pdf

 

[loosegravel]

Thanks billymade, this is awesome information. I will get to work and report back. It is still confusing to me how the code logs long after the engine is warm and the SAI system is shut off. I did read though in the information you provided that the system does go through a periodic "self test" indicating that it may actually try to turn on the relay, the air pump and activate the combination valve any time, weather cold or warm. Interesting system.