Manifold Pressure/Vacuum Sensor: Description and Operation

Manifold Absolute Pressure (MAP) Sensor:

PURPOSE
The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure. The pressure changes as a result of engine load and speed. The map sensor converts this to a voltage output.

OPERATION
A closed throttle on engine coast down would produce a relatively low MAP output voltage. A wide open throttle would produce a high MAP output voltage. This high output voltage is produced because the pressure inside the manifold is the same as outside the manifold. The MAP is inversely proportional to what is measured on a vacuum gage. The MAP sensor is used for the following:

^ Altitude determination.
^ Ignition timing control.
^ Exhaust Gas Recirculation (EGR) diagnostic.
^ Speed density fuel management default.