I have had a 2005 aveo automatic for a few years now and replaced the transmission recently because it went on me. Ever since I rebuilt the car it has had an engine light on, I took it to GM and they can't seem to clear the code (P300 2nd cylinder) they just say it is a misfire and that the car sometimes doesnt shift into 4th. Spark plugs and EGR have been changed. Any one had this code or know what I should do ? Thanks !