Manifold Pressure Sensor (Vacuum Sensor)


The manifold pressure sensor is used with D-type EFI for sensing the intake manifold pressure. This is one of the most important sensors in D-type EFI. By means of an IC built into this sensor, the manifold pressure sensor senses the intake manifold pressure as a PIM signal. The engine ECU then determines the basic injection duration and basic ignition advance angle on the basis of this PIM signal. As shown in the illustration, a silicon chip combined with a vacuum chamber maintained at a predetermined vacuum is incorporated into the sensor unit. One side of the chip is exposed to intake manifold pressure and the other side is exposed to the internal vacuum chamber.Therefore, high-altitude compensation correction is not required because the intake manifold pressure can be measured accurately even when the altitude changes. A change in the intake manifold pressure causes the shape of the silicon chip to change, and the resistance value of the chip fluctuates in accordance with the degree of deformation. The voltage signal into which this resistance value fluctuation is converted by the IC is the PIM signal.
If the vacuum hose connected to the sensor comes off, the fuel injection volume will reach the maximum, and the engine will not run properly. In addition, if the connector comes off, the engine ECU will switch to the fail-safe mode

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