Air Flow Meter/Sensor: Description and Operation

PURPOSE
The Mass Air Flow (MAF) sensor measures the amount of air that is ingested by a vehicles' engine. This information is required by the engine's Powertrain Control Module (PCM) to schedule fuel and maintain the desired air/fuel ratio.

OPERATION
The MAF sensor used on this vehicle is a hot wire type and is used to measure air flow rate. The MAF output frequency is a function of the power required to keep the air flow sensing elements "hot wires" at a fixed temperature above ambient temperature.

As air flows through the MAF sensor the "hot wires" are cooled. The amount of cooling is proportional to the rate of air flow. As air flow increases a greater amount of current is required to maintain the "hot wires" at a constant temperature. The MAF sensor converts the changes in current draw to a frequency signal read by the PCM. The PCM calculates air flow in (grams per second) based on this signal. A failure in the MAF circuit should set a Diagnostic Trouble Code (DTC) 48.