Manifold Pressure/Vacuum Sensor: Description and Operation

MAP Sensor Construction and Operation:

PURPOSE
The ECM uses the MAP sensor signal to sense engine load so that ignition timing and fuel delivery can be adjusted to maintain consistent engine performance.

LOCATION
The manifold absolute pressure (MAP) sensor is mounted in the control box.

CONSTRUCTION
The sensor consists of a silicon diaphragm and some support circuitry.

OPERATION
The ECM supplies a 5 volt signal and a ground to the sensor. A vacuum line supplies intake manifold vacuum to a small cavity under the silicon diaphragm which causes the diaphragm to flex. The flexing of the silicon generates a small voltage which is amplified by the support circuitry and used to modify the fixed 5 volt signal supplied by the ECM. The modified signal is then returned to ECM.