How to Test an Air Mass Meter


Air mass meters, more commonly known as mass air flow sensors or MAF sensors, are devices used in vehicle engines. They are used to determine and measure the amount of air that flows into a vehicle's engine. A hot wire element provides information to the vehicle's on-board computer on the air flowing into the engine by becoming cooler when more air enters the engine. However, the MAF sensor can become faulty over time and provide wrong information to the on-board computer. You can check your MAF sensor regularly by performing a few tests to determine if it is functional.

Things You'll Need

  • Ohmmeter
  • Voltmeter
  • 2 straight pins

MAF Sensor Test

  • Park the vehicle on a flat surface. Turn off both the ignition and the vehicle's engine. In many vehicles, turning the key in the ignition once will power the vehicle's battery. This allows the user to control electrically-powered devices such as the radio. Turning the key further will power the engine to start the vehicle. In this case, turn the ignition and the engine off. Disconnect and remove the electrical connector on the MAF sensor.

  • Connect the ohmmeter's positive probe on the MAF sensor terminal that is marked as "SIG".

  • Join the negative probe on the ohmmeter to the "GND" terminal on the MAF sensor.

  • Record the reading from the ohmmeter. If the reading indicates an infinite resistance or open circuit, the hot wire element of the MAF sensor is damaged.

Power Supply Test

  • Park the vehicle and turn on the vehicle's ignition. Do not start the vehicle's engine but ensure that the ignition is on.

  • Open the vehicle's hood. Determine the location of the MAF sensor and its electrical connector. Generally the sensor is located on the intake duct on the air filter housing in the front portion of the engine.

  • Disconnect the MAF sensor's electrical connectors. Join the voltmeter's negative probe to the sensor's GND terminal and the positive probe to the terminal indicated as "B+".

  • Record the voltage on the sensor. A voltage reading of zero indicates the MAF sensor may not be receiving any or enough electrical input from the vehicle's on-board computer, which means the MAF sensor is not functioning properly. There should generally be a steady fluctuation in the voltage if the MAF sensor is functional.

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  • Photo Credit Polka Dot Images/Polka Dot/Getty Images
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