The TPS (Throttle Position Sensor) is a potentiometer located above the throttle body. Its function is to detect the angle of the throttle lever. As this lever moves, the sensor sends a signal to the Powertrain Control Module (PCM).
This sensor has three wires, a 5-volt reference signal, a ground wire from the PCM (Powertrain Control Module) to the TPS (Throttle Position Sensor) and a return signal from the TPS to the PCM. The sensor returns the throttle position information to the powertrain control module via this same signal cable. When the throttle is closed the signal approaches 0.45 volts. In WOT (Wide Open Throttle) the voltage of the TPS signal approaches 5 volts in total. When the PowerTrain Control Module (PCM) observes a voltage that is out of the expected range, the fault code P0220 OBD2 is established.