P0 123 Throttle position sensing exceeds the upper limit circuit voltage is high.

The throttle position sensor is also called throttle opening sensor or throttle switch. Its main function is to detect whether the engine is in idle or load condition, acceleration or deceleration condition. It is essentially a variable resistor and several switches, which are installed on the throttle body. Its shape and internal structure are shown in the following figure.

The rotating shaft of the resistor is connected with the throttle valve, and it has two contacts: a fully open contact and an idle contact. When the throttle valve is in the idle position, the idle contact is closed and the idle working condition signal is output to the computer; When the throttle valve is in other positions, the idle contact is opened, and voltage signals with different angles relative to the throttle valve are output, and the computer identifies the engine load according to the signal voltage value; According to the change rate of signal voltage in a certain period of time, whether it is an acceleration state or a deceleration state is identified. According to these working conditions, the computer corrects the fuel injection quantity or controls the fuel cut-off.