Air Flow Meter/Sensor: Description and Operation

PURPOSE AND LOCATION
The air mass meter (located in-line to the air intake) sends a signal (current) to the fuel injection ECU. The ECU can now calculate the air mass entering the engine and adjust fuel injection duration as needed.
The air mass meter is of the hot-wire sensor type. Factors such as ambient temperature, humidity and pressure (altitude) are taken into consideration with this type of air meter.

OPERATION
The measurement sensor (inside the meter housing) consists of a wire (hot-wire) which is maintained at 120°C (250°F) higher than the air entering the engine. As the air mass passes over the hot-wire, wire resistance decreases and more current is required to maintain the correct temperature. The amount of current required is used to calculate the air mass entering the engine.
When the engine is turned off, any dirt on the wire is burned off electrically by a one second burn off cycle that heats the wire to 1000°C (1800°F). Any dirt remaining on the hot-wire can cause it to sent a faulty signal to the ECU.