Throttle Position Sensor

The Throttle Position (TP) sensor is a potentiometer connected to throttle shaft of throttle body. The TP sensor electrical circuit consists of a 5-volt supply line and a ground line, both provided by powertrain control module (PCM)/engine control module (ECM). The PCM/ECM calculates throttle position by monitoring voltage on this signal line. The TP sensor output changes as accelerator pedal is moved, changing throttle valve angle. At a closed throttle position, output of TP sensor is low, about 0.5 volt. As throttle valve opens, output increases so that, at wide open throttle (WOT), output voltage will be about 5 volts.

The PCM/ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent bursts of fuel from injector and an unstable idle, because PCM/ECM senses throttle is moving. A problem in any of TP sensor circuits should set a diagnostic trouble code P0122 or P0123. Once diagnostic trouble code is set, PCM/ECM will substitute a default value for TP sensor and some vehicle performance will return.