Mass Airflow Sensor

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/wire that is supplied with electric current from the ECM. The temperature of the hot film/wire is controlled by the ECM a certain amount. The heat generated by the hot film/wire is reduced as the intake air flows around it. The more air, the greater the heat loss.

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