What does throttle position sensor do?

A Throttle Position Sensor (TPS) in the Electronic Fuel Injection (EFI) system mainly determines the magnitude of the throttle valve's opening angle. This throttle position sensor uses a variable resistor to generate voltages by the magnitude of the throttle valve opening angle.

The Engine Control Unit (ECU) will provide a reference voltage of 5V as the input voltage. This voltage will flow through the variable resistor in the TPS. When the TPS is working, the 5V reference voltage will change due to a change in resistance in the variable resistor. The change in voltage that comes out from the TPS is called the output voltage. The ECU then uses this output voltage as input data to run the engine as it should.

This TPS is installed parallel to the throttle valve, so the more significant the throttle valve opening angle, the greater the output voltage from the TPS. The Engine Control Unit then interprets the change in the voltage generated by the TPS as the throttle valve opening angle in the throttle body.

The Throttle Position Sensor used in today's cars has also been combined with an idle switch component. The idle switch in this TPS is used to determine the engine's working position, whether the engine is idling or not.

If the idle switch is in the ON position (connected), it indicates the engine is idling. Meanwhile, if the idle switch is in the OFF position (disconnected), the engine is not idling.

What does the throttle position sensor do for the engine control unit while the engine is running? Well, in the following article, we will provide information about the throttle position sensor function. See the info below.

1. Determine the engine mode and conditions.

The throttle position sensor's function is to determine the engine mode and condition based on the magnitude of the throttle valve opening angle. The ECU will use at least three critical positions to select the actual engine mode. For example: when the throttle valve is fully closed, half-open, or fully open.

If the throttle valve position is fully closed, this indicates that the engine is off or idling. Meanwhile, suppose the throttle valve is in a half-open position. In that case, this means the engine is in a stable rotation condition (cruise) or an acceleration condition. If the throttle valve is fully open, the engine is in full load and accelerating.

The Engine Control Unit will read these positions from The Throttle Position Sensor's angles and then determine the ignition time and injection time required by the engine.

2. Turn off the AC switch and Emission control when the throttle valve is fully open

In addition to determining the engine's mode and position while working, another throttle position sensor function is an indicator of turning off the AC switch and controlling the exhaust emission system. This condition will be found when the throttle valve is fully open.

When the throttle valve is fully opened, it indicates that the engine is in full load or acceleration. The ECU uses this indicator to turn off the AC switch and control engine emissions to gain efficiency in fuel use.

3. Correcting the Air-fuel ratio

The next function of the throttle position sensor is as a reference for correcting the air-fuel ratio. Suppose the incoming air is read-only by sensors. In that case, this comparison correction is made on the fuel side by determining the length of time the injector valve opens when injecting fuel into the engine cylinder.

The ECU makes this correction based on data from various sensors, including the Throttle Position Sensor. The aim is to get an air-fuel ratio close to perfect, in the range of 1: 14.7.

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4. Correcting the presence or absence of an increase in engine power

The next function of the throttle position sensor is to make corrections to the presence or absence of an increase in power that occurs in the engine. Yes, in addition to determining the engine's position through the degree of the throttle valve opening, TPS also makes corrections when there is an increase in the engine's power. For example:

When the ignition is ON and the gas pedal is fully pressed. Currently, the ECU reads the engine condition that there is no increase in power or engine speed. So, the ECU still closes the injection valve in the injector to keep it closed. The goal is to keep the engine fuel-efficient.

5. Fuel cut control

The last function of the throttle position sensor that we knew was to control the fuel cut. This fuel cut means stopping the fuel supply injected by the injector into the combustion chamber by deactivating the injectors in all engine cylinders until the fuel cut conditions are passed.

This fuel cut control will occur when the engine is in a deceleration position. For example, the engine speed exceeds 2000 rpm, and the gas pedal is released suddenly. The throttle valve is fully closed. This fuel cut functions to reduce engine load and reduce exhaust emissions that occur when deceleration is carried out.