Air Flow Meter/Sensor: Description and Operation

Mass Air Flow Sensor:

The Mass Air Flow (MAF) sensor, located between the air filter and the throttle body, is used to measure the mass of the air entering the engine due to volumetric displacement.
The MAF sensor operates on the principle that if a mass is maintained at a constant temperature above the ambient environment, then the thermal loss is proportional to the mass flow of the cooling medium it is subjected to.
The electronic module of the MAF sensor heats a wire element to 392°F (200°C) above ambient temperature. As air passes through the sensor, the air cools the wire element. The MAF sensor supplies more power to the wire to keep it at a constant temperature difference. When a drop in power useage occurs, the MAF sends a signal to the Electronic Control Assembly (ECA) indicating the drop. The signal increases with the airflow into the engine.