My service engine light has been on since i bought the truck. it was supposedly and oxygen sensor and a fresh air pump in my emissions. But i never had it fixed because we have no emission laws in this state. so now my light has gone off on its own, and only comes on randomly or when im on the interstate and going at a good rate of speed and keep the engine above 3000rpm. i have 2 other post for problems with this truck. and the sh*tty thing is that my warranty is up and i start to have lots of problems.