Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. 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 the following circuits:

A 5-volt reference circuit
A low reference circuit
A TP sensor signal circuit

The PCM provides the TP sensor with 5 volts on the 5-volt 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 more than 4 volts through the TP sensor signal circuit. When the conditions for running this diagnostic trouble code (DTC) are met, the PCM will use the manifold absolute pressure (MAP) sensor in order 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.