Modern car engines are controlled by computers which regulate engine performance. Sensors are connected to major components which constantly send data to the computer which then adjusts performance accordingly to ensure minimal emissions and optimal performance. Reading data from these computers helps mechanics pinpoint where problems may lie in car performance. You can also find out this information with this OBD2 bluetooth engine code reader. It connects to your OBD2 port and will immediately intepret the information in the ECU (enging control unit). You can use this information to find faulty sensors which adversely affect performance, see if cylinders are misfiring, see how hot your engine coolant is, view engine RPMs and much more. Diagnosing and fixing certain problems yourself can save a lot of time and money. It's also fascinating to see how much engine information is readily available in modern cars. How it works: 1. Connect to your OBD2 port (common Apps to suit : Apple iOS, Android App name : Torque