Throttle Position Sensor: Description and Operation

Throttle Position Sensor:

The Throttle Position (TP) sensor is a potentiometer. The TP sensor is mounted to the right side of the throttle body. The TP sensor provides a voltage signal that changes relative to throttle blade angle. This signal voltage is one of the most important inputs used by the PCM. The TP sensor has a 5.0 volt reference, a ground and a signal circuit.

TP sensor Signal voltage should be about 0.6 volt at idle. The TP sensor voltage should increase to above 4.0 volts at wide open throttle (WOT). This diagnostic compares actual throttle position from the TP sensor to a predicted throttle position value. The predicted throttle position is calculated from engine speed and other inputs. If the PCM detects the predicted throttle position is below the actual TP sensor value, DTC P0121 will set.