I have a 2007 Chevy Cobalt with a 2.2 Liter engine with 4 cylinders. For a while my "Check Engine" light has been on and for the last couple of months it began to flash, which in the manual states that there's a misfire. Well I've done process of elimination such as tuning up completely; new AC Delco spark plugs, a brand new coil for the fourth cylinder, added fuel treatment twice, changed the air filter and the oil. After all this, the Check Engine light remains on and the Service Traction light is on. Two questions: One, is it something that I am missing and two, could the O2 Sensor be the cause of it?
