Throttle Position Sensor: Description and Operation

Throttle Position Sensor:

PURPOSE
The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the Powertrain Control Module (PCM) calculates throttle position. As the throttle valve angle is changed (accelerator pedal moved), the TP sensor signal also changes.

OPERATION
At a closed throttle position, the output of the TP sensor is low. As the throttle valve opens, the output increases so that at Wide Open Throttle (WOT), the output voltage should be above 4 volts.

The PCM calculates fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor may cause intermittent bursts of fuel from an injector and unstable idle because the PCM thinks the throttle is moving. A problem in the TP sensor 5 volts reference or signal circuits should set either a Diagnostic Trouble Code (DTC) P0122 or DTC P0123. A problem with the TP sensor ground circuit may set DTCs P0123 and P0117. Once a DTC is set, the PCM will use an artificial default value based on Mass Air Flow (MAF) for TP sensor and some vehicle performance will return. A high idle may result when either DTC P0122 or DTC P0123 is set.