I have a P0456 engine code which means I have a small leak in the evaporative system. What is the evaporative system? I know the basics on maintenance (starter, alternator,oil changes, etc...) but i'm not sure about the evaporative system.

 

its basically a vent for the vapours in your gas tank when the truck is running it vents these vapours through the charcoal canister it also puts these vapours back into ur intake system to be burned again its really hard to explain but thats the basics

 

Gaddy most of the time it is a loose gas cap or leaky gas cap. Try tightening it down then resetting the code and see if it comes back if it does try replacing the cap with a new one...