Air Flow Meter/Sensor: Description and Operation

Fig. 98 Air Flow Meter:

A portion of the intake air passes over a piece of hot film in the air flow meter. The ECU will maintain the hot film at a certain temperature. The air passing over the film will try to cool it, the ECU senses the amount of voltage needed to keep the wire at a certain temperature and transforms it into the air flow rate. The more air passing over the wire the more it is cooled, thus more voltage is required to keep it at a certain temperature.