MP4.2+6.0

The codes you see for it often talk about things like insufficient flow from one side or other, so I don't think it is as simple as run time. Theory of system is to pump extra air in along with more fuel to allow secondary combustion post cylinder and heat the cats more quickly. A combo of both air and fuel in terms of how it works, and a guess is if O2's don't see it right in this phase, you get the codes. Also combi valves are cycled hot in a self check IIRC to be sure EGR portion is also working.

supersam

Alright,

here's an update. THis morning, i started the car with leads tapped into the air pump and my scanner with live data monitoring the car; primarily monitoring coolant temp and air pump command. I had the air pump running on its own for about 70 seconds, and as soon as the coolant temp hit 50c, the air pump command went to off, which is when i immediately applied my outside power source to the air pump. Well,,,, about 5 minutes of the pump running like a champ, I got 2 codes (insufficient air flow to both banks). I honestly don't think i would have ever got these codes without running the pump for an extended period of time. So i guess it needs an air pump. Odd thing is; this thing was blowing like a leaf blower with the plug disconnected; maybe a new one would be slightly stronger. I'll continue to keep the forums updated in the event someone else has this same issue in the future.

MP4.2+6.0

Actually still not completely clear, but a likely. And maybe you just want to be done or smog check deadline in your face. BTDT. If so BTW, besides fast ship from on line dealer like audiusaparts.com in Portland Oregon, OES for pump is likely Pierburg. Then knowing that you can get OE quality for less than even discounted dealer via AutohausAZ (two days to Bay Area for me usually, though late week is harder w/ UPS, etc.), RockAuto and sometimes Amazon.

Again though, also look for anything that causes issues system wide/both heads ("banks"). Clogged or kinked hose issues on intake side of pump can do it. Any vacuum switching that controls both valves (like it did on my C5 4.2) can do it, etc. Unlikely, but I suppose even a horrendously clogged main air filter (or crap in hose intake for it inside box...) could do it since it first gets its air from there.

richard-tx

My guess is that the blower is fine but either the plumbing or the sensor is defective.