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How the Manifold Absolute Pressure Sensor (MAP Sensor or Vacuum Gauge) Works

Model: (Various brands) Various
Part: Checks and maintenance

Video tutorial

This sensor measures the absolute pressure in the intake manifold, which varies based on the engine load. The ECU uses this data along with others, such as engine RPM and air temperature, to accurately calculate the amount of fuel to inject and the optimal ignition timing.

Technically, it contains a piezoresistive silicon chip mounted on a diaphragm: one side is exposed to manifold pressure, while the other is sealed in a vacuum reference chamber. The pressure difference between the two sides deforms the silicon diaphragm, which in turn changes the electrical resistance of the chip.

An integrated circuit within the sensor converts this variation into a variable voltage signal. The output analog signal increases linearly with absolute pressure.

It is one of the most important sensors in the engine, as it measures engine load regardless of atmospheric altitude (for example, when driving in the mountains) and has a safety function, as an out-of-range MAP signal can cause the ECU to enter protection mode to prevent engine damage.


Posted on 14 July 2026 by ScegliAuto


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by ScegliAuto

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