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The intake pressure sensor is also known as the intake manifold pressure sensor. Applied to D-type electronically controlled fuel injection systems (L-type uses an air flow meter to detect intake volume). The intake pressure sensor is generally installed behind the throttle valve, and it calculates the amount of intake air by detecting the pressure changes behind the throttle valve. Its function is to detect pressure changes in the intake manifold and convert the intake pressure of the engine’s intake manifold into an electrical signal. Like the air flow meter, it is an important parameter that the engine control unit ECU uses to calculate the basic fuel injection amount and determine the optimal ignition timing. Common intake pressure sensors include analog, digital, and TMAP types. Both analog and digital systems have three wires: one for power, one for ground, and one for the signal. In contrast to these two, TMAP has an additional signal line for the temperature sensor. The TMAP-type intake manifold pressure sensor incorporates a temperature sensor; the engine control unit compares the intake air temperature with the boost pressure temperature, and if the temperature difference is greater than 8 degrees Celsius, it activates the coolant circulation pump. We used an oscilloscope to measure the signal from the simulated intake pressure sensor of the 2007 Mazda model with a 2.3L engine. Connect a BNC-to-banana plug cable to channel 1 of the oscilloscope; connect the black banana plug to a alligator clip in order to ground it to the negative terminal of the battery, and connect the red banana plug to a probe that is connected to the signal output terminal of the sensor. Set the oscilloscope channel attenuation to 1X, the vertical scale to 500ms/div, and the time base to around 500ms. To avoid interference from waveform glitches, the oscilloscope can be set to a 30K low-pass filter, after which the accelerator can be pressed quickly, taking the engine from idle to full throttle, in order to observe the waveform. The signal voltage of an analog pressure sensor changes as the engine vacuum level changes. At idle, the throttle is close to vacuum, indicating that it is almost closed at this time. As the air intake increases, the vacuum level decreases, the pressure increases, and the waveform moves upward. The principle is that the higher the absolute pressure in the intake manifold, the greater the deformation of the silicon diaphragm, with this deformation being proportional to the pressure. When the sensor structure and input voltage remain constant, the higher the pressure applied to the circular silicon wafer, the higher the output voltage. Typically, the output voltage of the intake pressure sensor is 1.25V at idle, slightly below 5V when the throttle is fully open, and close to 0V during full deceleration. Digital intake pressure sensors, such as those found in Ford engine control systems, have a signal frequency that changes as the engine’s vacuum level changes (usually in the form of a square wave signal); however, the voltage signal remains constant regardless of how the engine’s vacuum level changes.