Circuit Description

The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load (intake manifold vacuum) and RPM changes. The MAP sensor converts these changes into a voltage output. The Engine Control Module (ECM) sends a 5 volt reference voltage to the MAP sensor. As the intake manifold pressure changes, the output voltage of the MAP sensor also changes. A low voltage (high vacuum) output of 1 - 2 V is present at idle. A high voltage (low vacuum) output of 4.0 - 4.8 V is present at wide open throttle. A large quantity of air entering the engine indicates and acceleration or high load condition while a small quantity of air indicates a deceleration or idle condition. Under idle conditions, the MAP estimate correction is a weighted difference between the predicted MAP and the actual MAP reading.