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VW Passat 2002 4cyl manual secondary air flow

I have a major issue with the check engine light repeatedly coming on. The first time I happened to be at the dealer and they said that nothing was amiss, turned it off and I left. A few weeks later it came back on and I went to a local independent honest reliable mechanic. They have now seen the car three times and spent hours each time exhaustively going through the secondary air flow system (the light always indicates the same code) and have pretty much given up. Unfortunately, I need to get the car inspected in May and want to resolve this. Is it possible it’s a computer error? Anything subtle that anyone has heard on this subject?

The most common failure is the 50A fuse for the pump. This is caused by the second most common failure, the pump itself. A likely suspect a lazy oxygen sensor, because that is how the car knows if the pump is working. The least likely cause is the computer unless there is an update for the programming. Knowing the code and what the mechanics have checked would help answer your question.

The first time I took the car to the dealership and they said that everything checked out ok, turned off the light and sent me on my way. They did not provide the code.

The light came back again and I went to a local mechanic. The code was P0411.
They replaced a hose.

A few days later the light turned on again, same code. They spent many hours tracing the system and replaced the combo valve (and I think another hose).

A few days later the light turned on again (we turned it off, inconvenient timing). The following week it turned on again (same code every time) and they replaced the vacuum switching valve. Once again, it turned on again after a few days.

In all fairness to the mechanice, they didn’t charge me for the vacuum switching valve and the repeated diagnostic but they are out of ideas and cursing volkswagon.

Any suggestions are welcome.