F 150 2WD Pickup V8-4.6L (2002)
Air Flow Meter/Sensor: Description and Operation
Mass Air Flow Sensor
Typical Mass Air Flow (MAF) Sensor
Diagram Of Air Flow Through Throttle Body Contacting MAF Sensor Hot And Cold Wire Terminals
The Mass Air Flow (MAF) sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire
causes it to cool. This hot wire is maintained at 200°C (392°F) above ambient temperature as measured by a constant cold wire (Figure 35). If the hot
wire electronic sensing element must be replaced, then the entire assembly must be replaced. Replacing only the element may change the air flow
calibration.
The current required to maintain the temperature of the hot wire is proportional to the air mass flow. The MAF sensor then outputs an analog voltage
signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired
air/fuel ratio (Figure 36). This input is also used in determining transmission Electronic Pressure Control (EPC), shift and torque converter clutch
scheduling.
