Manifold Absolute Pressure Sensor
WARNING: This page is about a different car, the 2003 Saturn LW200 and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.
The Manifold Absolute Pressure (MAP) sensor measures changes in manifold pressure. Changes in manifold pressure result from engine load and speed changes. The MAP sensor converts these changes in manifold pressure into a voltage output signal to PCM (less than 2.0 volts at idle to about 4.0 volts key on engine not running at WOT). The PCM can monitor these signals and adjust air/fuel ratio and ignition timing under various operating conditions.