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The car’s accelerator pedal position sensor converts the amount of depression of the pedal (angle) into a voltage signal, thereby providing the engine control unit with information on the actual angle at which the accelerator pedal is pressed. Its working principle is that the engine control unit supplies a 5V voltage to the accelerator pedal position sensor, which in turn sends two voltage signals reflecting the position of the accelerator pedal to the engine control unit. When the engine is started and the accelerator pedal is not pressed or is only lightly pressed, the throttle valve opens to a fixed position under the control of a preset program; the engine control unit uses this signal to control the start-up process. There are two types of accelerator pedal position sensors: linear type and Hall element type. New engine electronic control systems increasingly use fully electronic throttle valves. To work with these valves, a accelerator pedal position sensor is required; this sensor converts the driver’s input into a voltage signal. Once this voltage signal is sent to the engine control unit, it generates signals to drive the throttle valve motor, thereby enabling control over the engine’s power output. The accelerator pedal position sensor is located in the engine compartment and is connected to the accelerator pedal via a cable. The sensor consists of two potentiometers inside; these potentiometers generate two signals, which are both sent to the engine control unit. The engine computer monitors these two voltage signals simultaneously; if the throttle opening indicated by these two signals is the same, it executes the command ； If there is a discrepancy, engine acceleration is restrictively limited for protection. Let’s take a look at how to measure the signal from a car throttle pedal sensor using an oscilloscope: http://www.micsig.com.cn/BBS/data/attachment/forum/202007/14/171907vft8v6l4f46d2vdl.jpg Connect a BNC-to-banana plug cable to channel 1 of the oscilloscope. Connect a black alligator clip to the black terminal (negative pole) of the test wire, and connect it to an appropriate ground point. Connect a pin to the positive terminal, and insert it into one of the potentiometer wires in the accelerator pedal sensor plug. Connect a BNC to banana plug cable to channel 2 of the oscilloscope. Connect a pin to the positive terminal, and insert it into the other potentiometer connection wire of the accelerator pedal sensor plug. If there are appropriate car leads, they can be used to replace the piercing method. After establishing the connection at http://www.micsig.com.cn/BBS/data/attachment/forum/202007/14/171907w86868ukbkdnw78d.jpg, set the channel attenuation for channels 1 and 2 to 1X, and set the vertical scale to 1V or 500mV. If the oscilloscope has high-pass and low-pass functions, enable the low-pass filter at 30KHz and set the time base to 500ms. Some oscilloscopes come with built-in automotive package software that allows for one-click setup. After setting it up at http://www.micsig.com.cn/BBS/data/attachment/forum/202007/14/171907ojq2j2fh3qkjqj0w.jpg, start the car and press the accelerator pedal; under normal conditions, the oscilloscope will display the signal waveform from the accelerator pedal sensor. The accelerator pedal position sensor is a potentiometer-type sensor. It receives two reference voltages from the Power Control Module (PCM), along with two ground wires and two signal wires (the signal wires transmit voltage changes related to the accelerator pedal position to the PCM). This is the signal voltage sent back to PCM; it varies depending on the vehicle, but it will never be higher than 5V. http://www.micsig.com.cn/BBS/data/attachment/forum/202007/14/171907io3zssdu1o6ynff7.jpg