Mass Air Flow (MAF) Sensor: Operation

The MAF sensing element consists or two temperature sensors symmetrical to a heating area sitting on a thin membrane. Up and down stream sensors see the same temperature when there is no air flowing through the sensor. With incoming flow, the upstream heating area is cooled down due to heat transfer, while the downstream area retains it's temperature because the air has been heated up after it flows through the heating area. The characteristic of temperature change in relation to airflow at the upstream area is utilized to determine the mass airflow passing through the sensor. This signal voltage variation is used by the ECM along with internal calibrations to coordinate the total mass air flow.

To reduce contamination during sensing, a partial air flow is directed at an angle with respect to the main flow in the measuring channel for the fact that moisture and other particles tend not to react in the same manner that air does after they hit the channel wall. The Diesel Power Relay supplies battery power the to MAF sensor, ground is provided by the ECM. The MAF sensor signal is provided by the ECM.