Air Flow Meter/Sensor: Description and Operation

PURPOSE
The Mass Air Flow (MAF) sensor detects intake air quantity and converts the measurement to a voltage reading. The voltage signal is sent to the Powertrain Control Module (PCM) which determines injection quantities and engine speed.

OPERATION
If air mass is maintained at a constant temperature above the ambient environment, then thermal loss is proportional to mass flow of the cooling medium it is subjected to. PCM heats a wire element above ambient temperature. As air passes through the sensor, the air cools the wire element. The PCM supplies more power to the wire to keep it at a constant temperature difference. When a drop in power useage occurs, the sensor sends a signal to the PCM indicating the drop. Signal increases with airflow into the engine.

CONSTRUCTION
Measurement of air quantity by means of a heated resistor.