DTC P0121: TP Sensor Performance: Description

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with the a 5-volt reference, a low reference and a signal circuit.

The PCM provides the TP sensor with 5 volts on the reference circuit and a ground on the low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to greater than 4 volts through the TP sensor signal circuit. When the Conditions For Running 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. If the PCM detects the TP sensor voltage is out of the predicted range, DTC P0121 sets.