DTC P0121: Throttle Position Sensor Performance: Description

The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of TP sensor rotor from closed throttle position to Wide Open Throttle (WOT) position provides PCM with a signal voltage from less than one volt to greater than 4 volts through the TP sensor signal circuit. When conditions for running this DTC are met, PCM will use the MAP sensor to determine if the predicted operating range of TP sensor is correct.

A skewed MAP sensor may cause this DTC to set and should be tested for proper operation if TP sensor is determined to be operating properly and this DTC continues to set.