Your barometric sensor may fail intermitently, triggering the CEL until someday it fails completely. It's subject to a lot of vibration from the location at the right front hood latch. It helps keep the fuel mixture adjusted to achieve better mileage and performance. Not a big issue unless you're driving in the mountains but the CEL is an annoyance. You can replace the sensor yourself in a couple minutes but I don't know if the code will clear itself. I believe they cost around $160.