E39 M5 - Secondary Air Injection System

[Roan]

Following up my post on M5Board and due to limited response I'm throwing this one out to the PH massive:

Whistling noise under light throttle at speeds of more than around 50mph. Let off throttle completely and noise goes away, depress the throttle any way past 50% or so and the sounds disappears too. Took the airbox, intake hoses and top plenum off to check for obvious leaks, and tested with carb cleaner and Propane with no indication of a problem. I can't reproduce the noise unless under load (and hence moving) though. I plan to take apart the lower plenum to get at the throttle bodies/gaskets etc BUT...

... I also have a P0411 Secondary Air Injection System Incorrect Flow Detected code (I've read in depth about carbon build-up etc.) and am wondering if this could be the source of the whistling? Would secondary air pump failure/leak/carbon build-up cause a whistle at part throttle under load?

[E38]

I have a very similar noise in mine. No fault code tho. I assumed its just one of those 'they all do that sir' things. Will keep a keen eye on this thread. It can be very annoying!

[Roan]

I have read elsewhere and in relation to different marques that there is a chance the whistle and the CEL code can be related due to vacuum leak, faulty pump, solenoid or valve but nothing specific on the M5. Driving me nuts!!

[Roan]

E38 said:

I have a very similar noise in mine. No fault code tho. I assumed its just one of those 'they all do that sir' things. Will keep a keen eye on this thread. It can be very annoying!

Chances are it's a vacuum leak somewhere from airbox to throttle body.

[corradokid]

Secondary air injection should only run when cold and is basically there to heat cats up quicker. does sound like you have an air leak maybe dirty throttle body ect.