Air Flow Meter/Sensor: Description and Operation

Airflow Meter:

PURPOSE
Measures incoming air volume and signals the ECU.

LOCATION
Attached to air cleaner assembly on left side engine compartment.

OPERATION
Meter measures air flow with a potentiometer rotated by a spring loaded measuring plate. Incoming air moves the measuring plate in relation to volume (more air, more movement), overriding spring tension. As the measuring plate moves, contacts in the attached potentiometer also move, varying potentiometer resistance and the input voltage signal sent to the ECU.

Incorporated into the air flow meter is a fuel pump switch and an intake air thermosensor. The fuel pump switch prevents fuel pump operation when the engine is not running and the ignition switch is ON. The thermosensor measures ambient air temperature to allow ECU fuel compensation based on air density.

The ECU factors intake air temperature into its fuel quantity calculations because density varies with temperature (cold air is denser than warm). With both flow volume (measuring plate and potentiometer) and temperature information, the ECU can make precise mixture adjustments under a wide range of operating conditions.