DTC P0121: Throttle Position Sensor Range/Performance: Description
WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
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 3 circuits:
- A 5-volt reference circuit.
- A low reference circuit.
- A TP 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 position provides the PCM with a signal voltage from less than 1 volt to greater than 4 volts through the TP sensor circuit. When the 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. If the PCM detects the TP sensor voltage is out of the predicted range, DTC P0121 sets.