Throttle Position Sensor: Operation

• The throttle position sensor functions to convert the degree of opening of the throttle valve to voltage, and to input the voltage (as signals) to the engine control unit. The engine control unit, based upon those signals, then regulates the amount of fuel injection, etc.
• The 5-volt power supply within the engine control unit is supplied to the throttle position sensor, after which it passes through the resistance within the sensor and is grounded at the engine control unit. See Fig 1 .
• When the throttle valve shaft is rotated all the way from the idling position to the fully open position, the resistance between the throttle position sensor's variable resistance terminal and the ground terminal also increases in accordance with that rotation, and, as a result, the voltage of the throttle position sensor's variable resistance terminal also becomes higher in accordance with that rotation.

Fig 1: Identifying Throttle Position Sensor Circuit

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.