DTC P0121: Throttle Position Sensor Circuit Insufficient Activity: Description

Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the 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 more than 4 volts through the TP sensor signal circuit. When conditions for running this DTC are met, the PCM will use the Manifold Absolute Pressure (MAP) sensor to determine if the predicted operating range of the TP sensor is correct. A skewed MAP sensor may cause this Diagnostic Trouble Code (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.