Mass Air Flow Sensor
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2004 Ford RV Cutaway, 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, and 2004 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.
The mass air flow (MAF) sensor provides an analog voltage signal to the PCM proportional to the intake air mass. The MAF sensor utilizes a hot wire sensing element to measure the amount of air entering the engine. The hot wire is maintained at 200° C (392° F) above ambient temperature. Air passing over the hot wire cools the wire. The current required to maintain the temperature of the hot wire is proportional to the air mass flow. The MAF signal is used to calculate exhaust gas recirculation (EGR) and for fault detection.