Exhuast Valve and Fan 2005 GMC Envoy

I've got a 2005 GMC Envoy with 4.2L 6 cylinder with 54K miles.
I recently noticed a high pitched whine that starts up when I start
the car cold and then winds down after about 20 seconds. It sounds like some bearings failing in a motor some place.
I took it in to my local mechanic to look at he and he says I have an exhaust fan inside the exhaust system and a check valve that prevents vapor flow back into the engine on start up and that the valve and fan have failed.. and that it's about $600 for parts and labor to replace.
Anyone ever hear of such valves and fans and know anything about them? He says it's just below the drivers door which is why I noticed it so quickly.
Thanks in advance for any info.
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Steve L wrote:

It sounds like you are talking about the secondary air pump, but it is located at the front of the vehicle. I've never heard them make noise, but I've never seen one when they start to fail. They are usually full of water and set up when they get to me. Nobody ever fixes them until they need to pass inspection.
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Hi Steve, yes I think that is what it is called.
It may not be completely failed yet, no check engine light or anything. But it is whining like it has bearings going in a small motor.
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Steve L wrote:

I had that happen on an old Monte Carlo (not mine but a friend's.) Sounded much like a squeaky belt, but it was the bearings in the AIR pump not the belt slipping. Eventually it seized up completely one day, then the belt *WAS* slipping :( replaced it with one from a junkyard.
I didn't know anyone still used AIR pumps in 2005? seems odd to me, esp. since didn't the Envoy use that then brand new DOHC straight six? You'd think that a clean sheet engine like that wouldn't need band-aids like an AIR pump to pass smog.
nate
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Nate Nagel wrote:

"Clean Sheet"! Har har!
GM and clean sheet do not compute. I own a Trailblazer. It's the most expensive '55 chevy ever made. All systems are a hack and my '03 example is pure junk. The only thing modern about that truck is the fact that it was designed to be assembled cheaply. Al
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wrote:

Anything specific you can list??
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