Mass Airflow (MAF) Sensor
MAF sensor uses a hot wire sensing element to measure amount of air entering the engine. Air passing over the hot wire causes it to cool. The hot wire is maintained at 392°F (200°C) above ambient temperature, as measure by a constant cold wire. See Fig 1 .
The current required to maintain hot wire operating temperature is proportional to the intake air mass. The PCM calculates the fuel injector pulse width in order to provide the desired air/fuel ratio.