Manifold Absolute Pressure (MAP) Sensor

MAP sensor is connected to ECM by a wiring harness and to engine by a manifold vacuum hose. The ECM supplies a 5-volt reference signal to MAP sensor. The MAP sensor voltage varies according to changes in engine load (manifold vacuum). The ECM interprets voltage change as a change in the engine load and uses signal to help determine control of fuel injector. The MAP sensor also measures barometric pressure, which allows ECM to automatically adjust for different altitudes. This eliminates the need for a separate sensor. On Prizm, ECM uses MAP sensor to control ignition timing.