Adopted as a government mandate to lower emissions, the "Check Engine" light comes on when a vehicle’s computer detects a problem that impacts emissions output. All 1996 and newer cars, light trucks, SUVs and minivans manufactured for use in the U.S. have this technology. It can signify anything from a loose gas cap to a major car repair expense. With CarMD, you can diagnose the problem yourself and more importantly, receive an estimation of the cost to fix it. Access to this information can save you time and money, especially when reviewing your mechanic’s repair estimate.