Throttle Position Sensor: Description and Operation

The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the PCM calculates the throttle position. As the throttle valve angle changes when the accelerator pedal is moved, the TP sensor signal also changes. At a closed throttle position, the output of the TP sensor is low.

As the throttle valve opens, the output increases so that at wide open throttle, the output voltage should be more than 3.3 volts.

By monitoring the output voltage from the TP sensor, the PCM can modify the fuel delivery based on the throttle angle. For example, power enrichment occurs when the throttle angle approaches wide-open throttle. The PCM looks primarily for changes in the TP sensor output to control fuel delivery. Acceleration enrichment occurs when the throttle angle increases, similar to an accelerator pump on a carbureted vehicle.