Throttle Position Sensor: Description and Operation

Purpose:
The throttle position (TP) sensor is mounted to the throttle body and connected to the throttle plate shaft. It senses the throttle valve angle and relays that information to the PCM.

Operation:
Knowledge of throttle angle is needed by the PCM to properly control injector control signals (pulses) and transmission gear selection. As the throttle valve rotates in response to movement of the accelerator pedal, the throttle shaft transfers this rotational movement to the TP sensor. The throttle position is a potentiometer with a five volt reference input and a signal ground supplied by the PCM. A sensor output signal to the PCM is a DC signal that varies according to throttle position angle. As the throttle angle changes the signal to the PCM varies.

At a closed throttle position, the output of the throttle position sensor is low (approximately 0.5 volt). As the throttle plate opens, the output signal increases so that, at wide-open throttle, the output voltage will be high (approximately five volts).

A noisy throttle position sensor at idle, varying more than four counts will disrupt closed loop engine idle control.