I am trying to identity a part on my 05 Blazer. - it is the box that almost looks like a battery box right behind the rear drivers side wheel under the truck next to the fuel tank. It is probably something to do with the fuel tank, just curious.

 

a picture might help.

 

It is a fuel vent canister full of charcoal to help reduce vapors escaping into the atmosphere.

 

fuel canister

 

Yep, EVAP canister or evaporative emissions canister (aka charcoal canister).

 

Cool, thanks guys. Is it possible to run without it? Not looking for laws or stuff like that, just wondering if the trucks performance will be effected.

 

If you do not plug the lines, you can have a vacuum leak as well as possibly a fuel smell.