scangauge code P0451?

Hey guys, on my way home today I had the check engine light come on, so I checked the codes, it came up with P0451. I looked up the code and it came up with this:

P0451 Evaporative Emission Control System Pressure Sensor Range/Performance

Where is this sensor and how critical is it? I wont be able to take it to the dealer for another week or 2, just trying to see how bad it is. I dont think its to bad but would like to make sure before I keep driving it around.

I just got my truck back from the dealer last friday after they replaced a bad charcoal canister and turned the light off. This seems pretty sudden..

 

Thanks for the info, so it should be ok to drive it for a week or 2 untill I get it to the dealer, correct?

btw gas cap is good, checked it as soon as I got out my truck, haha.

 

Did you ever get this fixed? What was the problem? Im getting the same code. I tested the evap with Techstream and it passed.