Since Sept, my check engine light has come on a total of 6 times. Every time, I bring it into the dealership to get it fixed. The first time, they told me it was a loose gas cap. The next couple times they said that different codes were coming up, and they continually fix something (they've changed the sensor in the gas tank, changed the filter in the front and the back of the car), but nothing seems to do the trick. This last time, I got the car back right before Halloween, and the light came on on Thanksgiving. Any ideas to what the problem could be?