Manifold Absolute Pressure (MAP) Sensor

MAP sensor is mounted on right side of engine compartment. This sensor is a variable resistance type which measures changes in intake manifold pressure which result from engine load and speed changes.

Pressure measured by MAP sensor is the difference between barometric pressure (atmospheric air) and manifold pressure (vacuum). Closed throttle condition (engine coast down) would produce low MAP reading while wide open throttle condition (engine acceleration) would produce high MAP reading. High value is produced because pressure inside intake manifold (vacuum) is same as pressure outside manifold (atmospheric air).

ECM supplies 5-volt reference signal to MAP sensor. As MAP changes, electrical resistance of sensor also changes. By monitoring sensor output voltage, ECM is informed of intake manifold pressure. Higher pressure (high voltage) requires more fuel, while lower pressure (low voltage) requires less fuel.