Air Flow Meter/Sensor: Description and Operation

Mass Air Flow (MAF) Sensor:

PURPOSE
The Mass Air Flow (MAF) sensor directly measures the mass of air flowing into the engine. The PCM calculates the required fuel injector pulsewidth in order to provide the desired air/fuel ratio, determining EPC, shift and torque converter clutch scheduling.


OPERATION

Mass Air Flow (MAF) Sensor:

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 Powertrain Control Module (PCM) 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.

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