Check engine code 456 on brand new '09

[kameele]

Got to work this morning and realized the CE light was on after only 1400 miles . i know a lot of cars this means that the gas cap wasn't tight. since I had filled up last night, I checked this and then tried again and it's still on. the local dealer said he couldn't look at it until friday, so I went to a VIP and they read the code. I then talked with a service guy at the dealer where I got it (not near work) he said if it is the gas cap and it's now nice and tight, it may take a couple days to clear. Something about a vacuum pump that gets checked a couple of times a day and its sensor that has to be happy for a few times after it's detected a leak Sure don't know much about how all that system works. does this sound like the way it should work? he did say that nothing in that code will hurt the car short-term, but to get it checked if it doesn't go away in a couple of days.

Thanks for any info.