Air Flow Meter/Sensor: Description and Operation

Air Flow Sensor:

PURPOSE
The air flow sensor measures all air entering the engine through the intake system. This information is vital to the ECM to determine proper fuel mixture and ignition control configurations.

CONSTRUCTION
A hot-film sensing head is used to measure air flow. Air flow is measured by determining the cooling effect on the sensing head.

OPERATION
Whenever the ignition is ON, the sensor produces an output signal to the ECM. The hot-film sensing head acts as a temperature sensitive resistor. The ECM maintains the sensing head at a preset constant temperature. As air passes over the hot-film, it has a tendency to cool. Since the sensor head changes resistance based on temperature, a varying current is required to maintain constant temperature. The internal circuitry of the sensor monitors this changing current demand and sends a varying voltage output signal to the ECM, tracking current required.