Throttle valve sensor

Throttle valve sensors are attached to the throttle valve axle. They capture the opening angle of the throttle valve and forward this information to the engine control unit as an electrical signal. The engine...

Function

Throttle valve sensorThrottle valve sensors are attached to the throttle valve axle. They capture the opening angle of the throttle valve and forward this information to the engine control unit as an electrical signal. The engine electronics uses this value to calculate the fuel quantity injected on the basis of other factors such as engine temperature, air pressure, speed, etc. Throttle valve sensors are available in a variety of designs:

Throttle potentiometer

Throttle switches

There are two switches inside a throttle switch. Each is actuated via a shift gate. The engine electronics uses the two switches to detect the two load conditions idling and full load. During idling the throttle valve and the idling switch are closed. At and above a fixed opening angle, the full load range starts and the full load switch is closed. When the full load switch is closed, the fuel injection quantity is increased to optimise performance.

Throttle potentiometer

With the throttle potentiometer, the opening angle of the throttle valve is captured with the assistance of a variable resistance. As there is a set ratio between the opening angle and the resistance value, the engine electronics can detect the angle of the throttle valve at all times. The angular velocity (i.e. the time in which the changes are made to the angle of the throttle valve) is captured at the same time. In the event of a rapid change (if the driver presses the accelerator pedal down quickly), the engine electronics will inject more fuel to achieve good acceleration.

Safety

The information from the throttle valve sensors is used, for example, to determine how much fuel should be injected. Therefore, the correct function of the throttle valve sensor is decisive for the safe operation of the engine. If the throttle valve sensor is faulty, the information from the accelerator pedal might not be interpreted correctly. In such cases, in critical driving situations, road safety can be impaired (if throttle response is delayed or peak performance is reduced, for example).

Depreciation

Throttle valve sensors are maintenance-free and are designed to last the service life of the vehicle. Since they respond to any changes to the accelerator pedal, they are, however, subject to mechanical wear. They are also extremely sensitive to soiling as a result of oil deposits, dust and moisture. Rubber seals prevent this to some extent, although conditions inside the engine compartment (extreme temperature differences, vibrations, oils, fuel vapours, cleaning agents, etc.) can cause the seals to become brittle. This can lead to malfunctions in the throttle valve sensors, with the following possible consequences:

  • Difficulties starting the engine
  • Speed fluctuations despite the position of the accelerator pedal remaining unchanged
  • Poor performance 
  • Increased fuel consumption 
  • Stuttering and bucking of the engine when the position of the accelerator pedal is changed.

By adhering to the maintenance intervals prescribed by the vehicle manufacturer and carrying out proper cleaning work inside the engine compartment, malfunctions in the throttle valve sensors and the associated problems can be avoided.

Environmental protection

The signals from the throttle valve sensors are vital for accurate fuel injection. As such the throttle valve sensors help to ensure that the correct fuel quantity is injected for the prevailing operating conditions and thus that the exhaust gas limit values prescribed by law can be complied with.

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