MAP Sensor Technical Information

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The logic module uses the manifold absolute pressure (MAP) sensor to determine the absolute pressure (not the relative to atmospheric pressure) of the air inside the intake manifold and the atmosphere (barometric pressure).
This information is used to determine the density of the air entering the combustion chamber (in conjunction with the IAT(Intake Air temperature) sensor), which is used when calculating the proper air/fuel mixture for the engine, especially at WOT since the system is not in closed-loop at this time.
It is also used to help adjust the IAC(Idle Air Control) motor during idle.

It uses a silicon wafer that is thinner in the centre (0.001") than around the edges (0.045"), which causes it to act as a diaphragm.
It is mounted with a perfect vacuum beneath the chip so that the air pressure from the other side flexes the chip.
This flexing causes a change in resistance and the circuitry inside the sensor converts this to a voltage ranging from 0.02V to 4.94V when the output is pulled up towards 5V by the ECM(Electronic control module).

1 Bar MAP sensors are used on NA(naturally aspirated) vehicles.
2 Bar MAP Sensors are used on forced induction vehicles(Turbo & Supercharged). They can measure up to 2x the atmospheric pressure(29.4psi), so that means it can measure up to 14.7psi boost (the atmosphere is 14.7psi + 14.7psi from the turbo/supercharger).

3 Bar MAP sensors can measure up to 44.1psi, which translates to 29.7psi boost from a Turbo/supercharger.

GM 8869004 466 2 Bar map sensor

A – Black/White

Ground

B - White

Sensor output

C - Red

+5v

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