Air Flow Meter/Sensor: Description and Operation

Air Flow Meter:

PURPOSE
Measures airflow into the engine and sends a signal to the ECU.

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

OPERATION
The air flow meter is a sliding cone type. The air flow meter consists of a measuring cone in a large venturi, supported by a light spring. Incoming air moves the measuring cone in proportion to the volume of air (more air, more movement). As the measuring cone moves, a sliding potentiometer attached to the cone also moves. The ECU reads the change in resistance through the potentiometer and calculates the volume of air entering the engine.

INTAKE AIR THERMOSENSOR
Incorporated into the airflow meter is an intake air thermosensor. It is a negative temperature coefficient thermistor. Negative temperature coefficient means as temperature increases, resistance decreases. Cold air is more dense than warm air. The ECU measures the resistance of the thermosensor and calculates the temperature of the incoming air. The ECU uses this info to make precise adjustments to fuel injection quantity and idle speed control to compensate for changes in air density due to changes in temperature.