... so I don't know what the error is this time. Its like the bypass valve stops working after some driving or something.

For those that have been following my negative deviation fault code error, I thought I solved it when I found a loose hose clamp (see link). The car had been running great for the past two weeks or so and then yesterday the code came up again.

So now I initiated the output diagnostics on the by-pass valve control module and its seems not right to me. Can anyone confirm.

When the output diagnostic is running on the by-pass valve control module, I hear a hissing noise coming from the back of the engine area. I also hear the by-pass valve operation working and the by-pass valve control module clicking. Then the by-pass valve operation gets quieter and then stops, the whole time, I hear the hissing and the by-pass valve control module still clicking away. I don't think the by-pass valve should slowly stop working under this test. The by-pass valve should continue to work as long at the by-pass valve control module is working. Its like it runs out of vacuum or something after a bunch of cycles.

I don't quite know where to look. I'm running in unchipped mode now, to see if I can get the fault code thrown but I don't think it will bacause there is not enough boost to have a large enough boost difference to throw the code. I almost want to start replacing vacuum lines.

Any comments or ideas?

Thanks,
Kirk<ul><li><a href="https://forums.audiworld.com/performance/msgs/52357.phtml">link to older post</a></li></ul>

 

Sounds like you have an N249 under the intake manifold that's supposed to control the bypass valve. That thing could be jacked. As a test, re-route the bypass valve vacuum line directly to the intake manifold and just loop the line that is normally on the intake manifold to the spot on the N249 valve is where the bypass valve normally connects.

I bet your output test of the bypass valve is simply using up the remainder of the vacuum stored in the vac reservoir and that's why the bypass valve operation fades away. I'd say that's normal. If you run the test again does it work? Or do you have to start the car to build up more vacuum for it to work again on the output test.

 

... and yes, it has the N249. Thats what I hear clicking.

I'm going to start replacing vacuum lines from the by-pass valve and see what that does.

The other thing is the N249 and the N112 (secondary air injection solenoid valve) are physically the same part so I might switch these two around (completely) and see what happens.

I think my test of the bpv is using up all available vacuum but unfortuenately you have to start the car before you can restart the output tests so the car builds vacuum back up. One thing I did try was to let the car sit over night and see if I cold do the output test straight away in the morning without starting the car and I could, there was still vacuum. I figure the leak must be after the by-pass valve control solenoid (N249).

I'm even entertaining the idea of picking up a hyperboost by-pass valve but I'm not sold on it yet.

Thanks for your input,
Kirk