Throttle Position Sensor: Description and Operation

Throttle Position Sensor (TPS):

Throttle Body Assembly - Exploded View:

Throttle Position Sensor Circuit Diagram:

DESCRIPTION
The throttle position sensor, mounted on the throttle body, relates throttle position to the ECM. The ECM uses voltage values from the throttle position sensor, compared with signals from the MAP sensor and ignition reference signals, to calculate engine load, for fuel injection and ignition timing control. Throttle position information is also important for determining when to output other functions such as acceleration and deceleration modes, purging the vapor canister, idle speed control, and others.

OPERATION
The Throttle Position Sensor (TPS) is connected to the throttle valve shaft in the throttle body unit. The TPS is a potentiometer with one connection to ground, and the other to the computer 5.0 volt reference source. A third wire from the computer is used to measure the output voltage from the TPS. As the throttle angle changes, the TPS divides the current from the reference source between the signal wire and ground varying the voltage in the signal wire from about 0.5 volts at closed throttle, to about 5.0 volts at wide open throttle. Each voltage value corresponds to a specific throttle angle. The computer monitors this voltage, calculates the throttle valve angle, and uses this information, compared with information from other engine sensors, to determine engine load, for fuel injection control, ignition timing, and other outputs.