A manifold absolute pressure, or MAP, sensor measures the pressure inside the intake manifold and sends a signal to the engine's electronic control unit. The electronic control unit uses this signal to adjust ignition timing and fuel enrichment, preventing engine damage and reducing fuel consumption.
The MAP sensor forms part of the modern engine control system. It provides manifold pressure information that the engine uses to calculate air density and determine the required fuel metering for optimum combustion. This information also influences the advance or retard rate of ignition timing. The electronic control unit converts the MAP sensor information into computable air mass data using the speed-density method.
When the electronic control unit reads a heavy load signal from the MAP sensor, it makes the engine fuel mixture denser than normal for the engine to produce more power. It also decelerates the ignition timing to prevent explosions that can affect vehicle performance. When the MAP sensor sends a light load signal to the control unit, the engine's control unit responds by leaning out the fuel mixture and accelerating the ignition timing to reduce fuel consumption.
The MAP sensor also works alongside with on-board diagnostic motor engine applications to test the functionality of the exhaust gas recirculation valve.