Why Do Mass Air Flow (MAF) Sensors Fail? - Engine Builder Magazine
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Why Do Mass Air Flow (MAF) Sensors Fail?


Drivers often notice sluggish performance,
rough idling, poor acceleration or even stalling. There may also be a more
frequent need to refuel. 

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Contamination could even occur as early as at every
18,000-25,000 miles, depending on the vehicle model. For example, with small or
compact cars, the MAF sensor can clog quicker, as it is placed in a smaller
engine bay subjected to more risk in critical areas (oil vapor flows and
combustion debris). In this case, a replacement becomes the equivalent of a
long drain oil service…it almost becomes a service-style repair.

Other common failure problems include:

• Contact fault at the electrical connections;

• Damaged measuring elements;

• Mechanical damage (vibrations, accident); and

• Measuring element drift (exceeding the measuring

A problem with the mass air flow sensor often causes the
”check engine” or ”service engine soon” light in the vehicle instrument panel
to illuminate. These lights come on when the engine computer detects some fault
in one of the components of the emission control system.


Symptoms of failure include:

• “Check engine” or “service engine soon” light is on;

• Hesitation/stall on rapid acceleration;

• Poor engine running at idle and/or surge;

• Excessive vibrations when stationary; and/or

• RPMs changing noticeably without driver input.

How to troubleshoot a MAF sensor:

The following steps should be taken into account during MAF sensor

• Check the connector for a correct fit and good contact.

• Check the MAF sensor for damage.

• Check the measuring elements for damage.

• Check the voltage supply with the ignition switched on (circuit
diagram for pin assignment is necessary). Ref. value: 7.5-14V

• Check the output voltage with the engine running (circuit diagram
for pin assignment is necessary). Ref. value: 0-5V

• Check the connection cables between the removed control
unit connector and sensor connector for transmission (circuit diagram for pin
assignment necessary). Ref. value: approx. 0 ohm.


• Conduct an electronic test of the MAF sensor by the engine
management control unit. If a fault occurs, a fault code is stored in the
control unit and can be obtained using a diagnostics unit.

Courtesy of Delphi Product and Service Solutions.

Engine Builder Magazine