Haltech 1 Bar GM MAP SensorDescription 1 Bar GM MAP Sensor Includes: Matching plug and 3 pins. Other Information: A Haltech MAP sensor (manifold absolute pressure) provides instantaneous pressure information to the electronic control unit (ECU) from the intake manifold the amount of boost or vacuum in the intake manifold. This is necessary to calculate air density and determine the engine's air mass flow rate or in other words engine load. Engine load is used as a reference for