Focus L4-2.0L SOHC VIN P (2000)
Air Flow Meter/Sensor: Description and Operation
Mass Air Flow Sensor
Typical Mass Air Flow (MAF) Sensor
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. 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. This input is also used in determining transmission Electronic Pressure Control (EPC), shift and torque converter clutch scheduling.
Diagram Of Air Flow Through Throttle Body Containing MAF Sensor Hot And Cold Wire (and IAT Sensor Where Applicable) Terminals
Some MAF sensors have Integrated Bypass Technology (IBT) with an integrated Intake Air Temperature (IAT) sensor. The present applications with
IBT are: Focus, Escort (4V), 2.0 L Contour/Mystique, Cougar, Taurus/Sable, Windstar, Explorer/Mountaineer and E-Series.
The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly.
