I am having difficulty trying to figure out what this is (see attached photo). there is hose coming out of it that is not attached to anything. this is in a 2001 blazer 4wd. Thanks for your help in advance!

 

I have no clue but now I want to know too!

 

If I'm not mistaken, it's an air injection pump. Another emissions crapola thing that luckily didn't seem to make it onto a lot of Blazers, at least from what I've seen...

 

Thanks, ill have to check it out

 

Yeah I would say air injection as well looking at those hoses. Have you followed the hoses to see where they go? Probably to the exhaust manifolds or somewhere in the exhaust system before the O2 sensor.

 

Its the A.I.R. pump. The big hose that is not hooked to anything is the air intake for the pump.

 

And if it's not working it causes codes to be thrown. I think like 410, 411 and my favorite 418. took me a couple months and trip to pick an pull to sort that out.

 

That is called the secondary air pump injection system and it can cause a check engine light and fail you on inspection in NC! I know have that problem!