Air Flow Meter/Sensor: Description and Operation

Mass Air Flow Sensor (MAFS):

PURPOSE
The Mass Air Flow Sensor (MAFS) measures the intake air flow rate by measuring a sample of the entire flow. Measurements are made in such a way that the Engine Control Module (ECM) receives electrical output signals which vary in relation to the amount of air flowing over the hot wire placed in the stream of the intake air.

OPERATION
Intake air flows into the intake manifold through a route around the hot wire. Heat generated from the hot wire is cooled by the air flow. The amount of heat reduction depends on the air flow. The temperature of the hot wire is automatically controlled to a certain number of degrees. More electric current is required to maintain the temperature of the hot wire as air flow increases. The ECM calculates air flow by means of this current change.

NOTE: A Diagnostic Trouble Code (DTC) will be stored for the MAFS if a failure in its circuit is detected by the ECM.

- Mass Air Flow Sensor DTC No. 12.