Manifold Absolute Pressure Sensor

The Manifold Absolute Pressure (MAP) sensor is connected to PCM by a wiring harness and to engine by a manifold vacuum hose. PCM supplies a 5-volt reference signal, a bias voltage and a ground to MAP sensor. MAP sensor voltage varies according to changes in engine load and engine RPM (manifold vacuum). Low voltage signal indicates low manifold pressure (high vacuum) and high voltage indicates high manifold pressure (low vacuum). PCM uses voltage signal to control fuel volume available.

On Prizm, MAP sensor is used to measure barometric pressure, which allows PCM to automatically adjust injector "on" time for different altitudes and to control ignition timing.