MAP Sensor.

 MAP Sensor Definition:

Absolute pressure is usually 1 atmosphere (1 atm) or 14.7 psi.

Refers to a manifold absolute pressure sensor, a variable resistor used to monitor the difference in pressure between the intake manifold at outside atmosphere.

This information is used by the engine computer to monitor engine load (vacuum drops when the engine is under load or at wide open throttle). When the engine is under load, the computer may alter spark timing and the fuel mixture to improve performance and emissions.