The purpose of Emissions testing is to make sure your vehicle is following the Federal Clean Air Act. Emissions testing measures the number of pollutants your vehicle gives off. If you take your vehicle to Emission and you fail, or your check engine light is on in most cases you will need an Emissions-related repair. After the repair is performed at a reputable automotive or diesel repair shop keep in mind your vehicle will usually run better and get better gas or fuel mileage.