Everytime I drive from Phnx to LA and I stop to get gas in Quartzsite AZ. or just east of State line my CEL light comes on right after I pull way from the pump. I dissconnect the battery in LA and then it comes on again when I fill up on the way home. I also think my mpg tanks a bit too, but not sure. What gives? Doesnt happen going anywhere else, Flag, LV, etc..