Mass Air Flow (MAF) Sensor

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2005 Mercury Sable, 2005 Mercury Mountaineer, 2005 Mercury Monterey, 2005 Mercury Montego, and 2005 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

The 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 the 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.

Fig 1: Cutaway View Of MAF Sensor

Courtesy of FORD MOTOR CO.

The current required to maintain the temperature of the hot wire is proportional to the mass air 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.

Most MAF sensors have integrated bypass technology (IBT) with an integrated intake air temperature (IAT) sensor.

The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly.

Fig 2: Typical Mass Air Flow (MAF) Sensor

Courtesy of FORD MOTOR CO.

Fig 3: Identifying Typical Drop-in Mass Air Flow (MAF) Sensor

Courtesy of FORD MOTOR CO.