Check engine light on twice in a row in a year for Scion Xa?

Hi all, I have a Scion Xa 06 and it has only 15,000 miles with only two years of use. Three days ago, the check engine light turned itself on (again) and I do not know what the problem is. Last time, the dealership told me that it is due to the parts located in the gas tank. I'm very upset about this especially when I bought it new and has only so few miles on it and usage. Is this normal for all Scion Xa vehicles? Why has this happened. I live in New York, so could it be due to the cold weather? I used to live in Seattle, where it is warmer and this never happened before