Throttle Position Sensor: Description and Operation

Throttle Position Sensor (TPS):

The Throttle Position Sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. The TPS electrical circuit consists of a 5.0 volts supply line and a ground line, both provided by the ECM. By monitoring the voltage on this signal line the ECM calculates throttle position. As the throttle valve angle is changed (accelerator pedal moved), the output of the TPS also changes. At a closed throttle position, the output of the TPS is low (approximately 0.5 volt). As the throttle valve opens, the output increases so that, at wide-open throttle, the output voltage will be approximately 5.0 volts. The ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TPS can cause intermittent bursts of fuel from the injector, and an unstable idle, because the ECM thinks the throttle is moving. A problem in any of the TPS circuits should set a Code 21. Once a trouble code is set, the ECM will use an artificial default value for TPS, and some vehicle performance will return. A high idle will result when Code 21 is set.