Throttle position sensor

The throttle position sensor is a device to detect the engine state.

Throttle position sensor, also known as throttle opening sensor or throttle switch, is a device for detecting engine state. 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.

What does the throttle position sensor detect?

Detection structure and circuit of throttle position sensor. The throttle position sensor with switch output is also called throttle switch. It has two pairs of contacts, namely idle contact IDL and full load contact PSW. A cam coaxial with the throttle valve controls the opening and closing of two switch contacts.

When the throttle valve is in the fully closed position, the idle contact IDL is closed, and the ECU judges that the engine is in idle working condition according to the closing signal of the idle switch, so as to control the fuel injection quantity according to the requirements of idle working condition; When the throttle valve is opened, the idle contact is opened, and the ECU controls the fuel injection under the transition condition from idle speed to light load according to this signal.

The fully loaded contact is always open from the fully closed throttle position to the middle and small opening. When the throttle is opened to a certain angle, the full-load contact begins to close, and a signal that the engine is running at full load is sent to the ECU, and the ECU performs full-load enrichment control according to the signal. Throttle position sensor with switch output in electronic control system of Toyota 1G-EU engine.