Manifold Absolute Pressure (Map) Sensor
The MAP sensor reacts to absolute pressure in the intake manifold and provides an input signal to the ECU. As the engine load changes, manifold pressure varies, which causes the MAP sensor resistance to change, resulting in a different input voltage to the ECU. The input voltage level supplies the ECU with information relating to ambient barometric pressure during engine start-up or regarding engine load while the engine is running. The ECU calculates this information and adjusts the air-fuel mixture accordingly.
The MAP sensor is mounted under the hood on the firewall and is connected to the throttle body with a vacuum hose. See Fig 1 .