The transmission ratio is the difference between the input speed and the output speed. The transmission ratio allows the vehicle to achieve high speeds while maximizing engine output power.
The ECM (Engine Control Module) or TCM (Transmission Control Module) uses the sensor input and checks the proper functioning of the transmission and its components. If the ECM states that the transmission ratio is outside the predetermined range, the Check Engine light is illuminated. The diagnostic code P0733 OBD2 is stored when shifting to or driving in third gear.