This calibration tool is the first of its kind. Compact and easy to use, the Accu Pro calibration tool plugs directly into your vehicles diagnostic port . Once plugged in, the Accu Pro calibration tool can read and clear the vehicle DTCs (diagnostic trouble codes), correct the part throttle shifting, as well as the speedometer and odometer readings when non-stock tire sizes and/or non-stock gear ratios are installed. No more wondering how fast you are travelling or what the true miles on your vehicle really are. Get accurate as required by law, get Accu Pro.