MAP Sensor

The MAP sensor measures the intake manifold vacuum. Under high fuel demands, such as wide open throttle, the MAP sensor senses low vacuum. The engine control module (ECM) uses this information to enrich the fuel mixture. Fuel injector on-time is increased to provide the correct amount of fuel. When decelerating the engine vacuum increases. This vacuum change is sensed by the MAP sensor and measured by the ECM, which then decreases the fuel injector on-time due to the low fuel demand conditions.