Air Flow Meter/Sensor: Description and Operation

The mass air flow sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the PCM. The temperature of the hot film is controlled by the PCM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss.

Therefore, the PCM must supply more electric current to maintain the temperature of the hot wire as air flow increases. The PCM detects the air flow by means of this current change.