Sensor, Mass Airflow (MAF): Operation

The Mass Air Flow (MAF) sensor is a frequency based device. A constant voltage is applied to a heated wire on the sensor.

• This wire is positioned in the air cleaner air stream and is heated by the electrical current that the voltage produces. As air flows across it, it cools down.
• The heated wire or film is a positive temperature coefficient resistor. This means that its resistance drops when its temperature drops.
• The drop in resistance allows more current to flow through it in order to maintain the programmed temperature.
• This current is changed to a frequency which is sent to the Powertrain Control Module (PCM) and interpreted as air flow.
• Adjustments for air temperature and humidity are taken into consideration because they also affect the temperature of the heated wire or film.