Air Flow Meter/Sensor: Description and Operation

Mass Air Flow Sensor:

PURPOSE
The Mass Air Flow (MAF) sensor directly measures the mass of air flowing into the engine.

LOCATION
Between the air filter housing and throttle body assembly.

CONSTRUCTION
The sensing element is a thin platinum wire wound on a ceramic bobbin and coated with glass.

OPERATION
The MAF operates on the principle that if a mass is maintained at a constant temperature above ambient, the thermal loss is proportional to the mass flow of the cooling medium it is subjected to.

The sensor output is a DC (analog) signal ranging from 0.5 to 5.0 volts used by the Electronic Control Assembly (ECA) to calculate fuel injector pulse width for stoichiometry (14.7 to 1). The "hot wire" is maintained at 392°F (200°C) above ambient temperature as measured by a constant "cold wire".

The lower the signal, the less airflow into the engine. The higher the signal, the greater the amount of airflow into the engine.