DTC P0121: Throttle Position Sensor Circuit Insufficient Activity: Description

The Throttle Position (TP) sensor is a potentiometer mounted on side of throttle body. TP sensor voltage signal changes relative to throttle blade angle. TP sensor uses a 5-volt reference, a ground and a signal circuit. TP sensor signal voltage should be about 0.6 volt at idle and 4 volts or more at wide open throttle. Powertrain Control Module (PCM) compares actual throttle position from TP sensor to a predicted throttle position value. The predicted value is calculated from engine speed and other inputs.