Theory of operation
WARNING: This page is about a different car, the 2011 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The Manifold Absolute Pressure (MAP) sensor is a transducer that varies resistance according to changes in altitude and atmospheric conditions. The MAP reading gives the Powertrain Control Module (PCM) an indication of the current air pressure within the intake manifold. The PCM uses this information to calculate fuel delivery. The MAP sensor has a 5 Volt reference circuit, a low reference circuit and a signal circuit. The PCM supplies 5 Volts to the MAP sensor on a 5 Volt reference circuit and provides a ground on a low reference circuit. The MAP sensor provides a voltage signal to the PCM on a signal circuit relative to the pressure changes.