P0411 Help!! Will not go away!

[Audimaster]

Hey guys!

Well my 98 A4 Quattro 2.8L has a P0411 fault code problem. Everything runs fine, but i need to pass an inspection soon and the check engine light will fail me, so will any emission problem.

I have read articles about how AIR pumps and combo valves can go bada....but there are alot of check valves and such on this car.

At this point, is there anything common I can check or replace myself?

I can hear something funny, perhaps exhaust sound at startup, but it only lasts a second or two.

UPDATE:: Using a vacuum pump and smoke machine I verified the following: used vacuum pump to confirm that the combo valves at rear of heads are opening by commanding them open.( at least a little).
Used a power probe to energize the solenoid control valve that applies vacuum to the combo valves. Seems to be commanding the valves open.

At this point, tomorrow when it is colder outside, I will attempt to make sure the ECM is commanding the solenoid control valve to open the combo valves. I have found NO vacuum lines or hoses with any leaks that my smoke machine could find. If the ECM IS commanding that valve, and it DOES open those combo valves then I am truly lost, as the system appears to work as the manuals say.

Any input would be greatly appreciated.


Thanks!
Mike