On Board Diagnostics

Mass Air Flow Sensor

Mass Air Flow (MAF) Sensor

The Mass Air Flow sensor is located in the intake air duct between the air cleaner and the throttle body. The MAF's function is to measure the volume and density of air entering the engine and outputs an analog voltage signal to the ECU proportional to the intake air mass. The ECU calculates the required fuel injector pulse-width for the correct air/fuel ratio.

Mass Air Flow Sensor

Basic Operation

The MAF sensor uses a heated element, such as a "Hot Wire" or "Heated Film", to determine the "mass" of the incoming air. A small passage inside the sensor directs part of the air flow past the heated element. As more air passes the heated element, heat is carried away by the passing air. As a result, more current is required to maintain the constant temperature of the element. The electronic module converts this electrical current flow into an analog output voltage which varies between .4 volts at low air flow to 5 volts at maximum air flow.

 A dirty or defective Mass Air Flow sensor causes ...

  • A lack of power, hesitation, or unstable idle
  • Engine stalls without warning, but usually restarts with no problem
  • Poor fuel mileage

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    Last Update: January 28, 2008