Throttle Position Sensor: Description and Operation

Throttle Position Sensor:

The Throttle Position Sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body assembly. TPS electrical circuit consists of a 5 volt supply line and a ground line, both provided by ECM. By monitoring voltage on this signal line, ECM calculates throttle position. As throttle valve position is changed, output of TPS also changes. At closed throttle position, TPS output is low (approximately .5 volt). At wide open throttle, output is high (approximately 4 volts).

A problem in any for TPS circuits should set Code 21. Once a Code is set, ECM will use default valve for TPS. High idle will result when Code 21 is set.