Manifold Pressure/Vacuum Sensor: Description and Operation

PURPOSE
The manifold absolute pressure (MAP) sensor measures intake manifold vacuum. The engine control module (ECM) uses this information to determine engine load.

CONSTRUCTION
The sensor contains a silicon diaphragm covering a small vacuum port. When vacuum is applied, the diaphragm flexes which causes a low voltage signal to be generated. An internal circuit amplifies the signal to produce a higher voltage back to the ECM.

OPERATION
Whenever the engine is running, the sensor produces a readable voltage. The voltage varies dependant upon the amount of vacuum present at the sensing port.