Manifold Absolute Pressure (MAP) Sensor
WARNING: This page is about a different car, the 1995 Ford Pickup, 1995 Ford F-Super Duty, and 1995 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Manifold pressure and temperature are used by the PCM to calculate the airflow rate. The MAP sensor responds to manifold vacuum changes due to engine load and speed changes.
The MAP sensor uses frequency to measure manifold vacuum. The MAP sensor is used as a barometric sensor for altitude compensation, updating the PCM during Key On, Engine Off (KOEO) and at Wide Open Throttle (WOT). By monitoring MAP sensor output voltage, the PCM can determine correct rate of spark advance, EGR flow and air/fuel ratio. If MAP sensor fails, the PCM will supply a fixed MAP value and use the Throttle Position (TP) sensor to control fuel distribution.