Throttle Position Sensor: Description and Operation

Throttle Position Sensor:

TPS:

PURPOSE
Informs the ECM with throttle valve position information.

OPERATION
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 of the TPS circuits should set a diagnostic trouble code (DTC) 21. Once a DTC is set, the ECM will use an artificial default value for TPS sensor. A high idle will result when DTC 21 is set.