I've got a 2001 Blazer LT 4.3L 4WD. I learned today when switching stickers from a replacement fan guard that my engine is equipped with an "A.I.R. module." I remember there being a strange air line that goes from the back driver side of the engine around the top and down near the bottom passenger side of the radiator, but I never realized what it was until I looked more closely at the engine specs sticker. The car isn't on the road right now so I can't get it to the shop and put it on the lift but I've been searching and all google turns up is results for airbag modules. On a Cadillac DHS I worked on it had an A.I.R. module that injects fresh air into the exhaust or something, is this the same system? I don't think there's any problem with mine but I'm curious what it's used for?

 

AIR = Air Injection Reaction. It is a system that pumps fresh air into the exhaust system to improve catalytic converter efficiency/effectiveness. The same system is used on many modern vehicles.