Just a tip.. before you visit the dealer or do anything else try to wipe the area of the gas cap. My SES light was coming on with P2402 code and I was resetting it every time but after 2~3 days it would come on again. After a few months of repeating that I read this thread and saw 330icanadian's comment above. After seeing his comment I wiped the gas cap area and reset the code. It's been two months now and the SES light is not coming back ever since.