Throttle Position Sensor: Description and Operation

Throttle Position (TP) Sensor:

DESCRIPTION
The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. The TP sensor electrical circuit consists of a 5 volt supply line and a ground line, both provided by the Powertrain Control Module (PCM), and a signal line to the PCM. By monitoring the voltage on this signal line, the PCM can calculate the throttle position angle in a percentage. As the throttle valve angle is changed (accelerator pedal moved), the output of the TP sensor also changes. At a closed throttle position, the output of the TP sensor is low (approximately 0.6 volt). As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be near 5 volts.

OPERATION
The PCM can determine the fuel delivery based on the throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent bursts of fuel from the injectors and an unstable idle, because the PCM thinks the throttle is moving. A high or low voltage problem in the TP sensor circuits should set either a DTC P0122 or DTC P0123. The PCM also has the capability of setting a DTC P0121 if the sensor is reading out of range. Once a diagnostic trouble code is set, the PCM will use a default value for the TP sensor, and some vehicle performance will return.