Here is a typical schematic diagram of the car Throttle Position . The (TPS) is designed to indicates the position of the throttle valve. Usually the is mounted on the throttle body and converts the throttle valve angle into an electrical signals. Inside the TPS is a resistor and a wiper arm. The arm is always contacting the resistor.

 Throttle Position Sensor Circuit Diagram

How the works?
A wiper arm inside the sensor is mechanically connected to a moving part, such as valve or vane. As the part moves, the wiper arm also moves. The wiper arm is also in contact with a resistor. As the wiper arm moves on the resistor, the signal voltage output changes which indicates position.

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