Ford Freestar, Monterey 2004-2006

Mass Air Flow (MAF) Sensor



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. 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.

The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly. Most MAF sensors have integrated bypass technology with an integrated Intake Air Temperature (IAT) sensor. The hot wire electronic sensing element must be replaced as an assembly. Replacing only the element may change the air flow calibration.

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Fig. Typical Mass Air Flow Sensor (MAF)

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Fig. Identifying air flow through throttle body contacting MAF sensor hot and cold wire terminals

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Fig. Typical Drop-in MAF sensor

Removal & Installation

  1. Disconnect the battery ground cable.
  3. Disconnect the Mass Air Flow (MAF) sensor electrical connector.
  5. Remove the 2 MAF sensor screws and the MAF sensor.
  7. To install, reverse the removal procedure. Tighten the MAF sensor screws to 89 inch lbs. (10 Nm).