Throttle Position Sensor: Description and Operation

Typical Throttle Position Sensor (TPS) Wiring:

The Throttle Position Sensor (TPS), is mounted on the side of the throttle body opposite the throttle lever assembly. Its function is to sense the current throttle valve position and relay that information to the ECM. Throttle position information allows the ECM to generate the required injector control signals (base pulse).

If the TPS senses a opening throttle, a voltage signal indicating this condition is sent to the ECM. The ECM then increases the injector pulse width, permitting increased fuel flow.
As the throttle valve rotates in response to movement of the accelerator pedal, the throttle shaft transfers this rotation to the TPS. A potentiometer (variable resistor) within the TPS assembly changes its resistance (and voltage drop) in proportion to throttle movement.
By applying a reference voltage (5.0 volts) to the TPS input, a varying voltage (reflecting throttle position) is available at the TPS output. For example, approximately 2.5 volts results from a 50% throttle valve opening (depending on TPS calibration). The voltage output from the TPS assembly is routed to the ECM for use in determining throttle position.

If the TPS is held in a wide open throttle (WOT) position during engine start, the ECM will interpret this as a clear flood mode. The ECM will then pulse the injectors at a ratio of 20 to 1 in order to clear a flooded condition. The ECM will hold this injector rate as long as the throttle stays wide open, and the engine speed is below 600 rpm.