10 Things You Should Know About MAF Sensors

10 Things You Should Know About MAF Mass Airflow Sensors

I’m doing additional study on the MAF sensor. Gather all of the pertinent information regarding this automobile sensor. This tutorial will teach us a lot. I hope this tutorial was useful to you.


A mass (air) flow sensor (MAF) measures the mass flow rate of air into a fuel-injected internal combustion engine.

The engine control unit (ECU) needs the air mass information to balance and supply the proper fuel mass to the engine. Temperature and pressure affect the density of air. Air density changes with ambient temperature, altitude, and the usage of forced induction in automotive applications, thus mass flow sensors are better than volumetric flow sensors for measuring the amount of intake air in each cylinder.

On automobile engines, there are two types of mass airflow sensors in use. The vane meter and the hot wire are these. Neither design makes use of technology that directly monitors air mass. An engine’s ECU, on the other hand, may calculate the mass flow rate of intake air using extra sensors and inputs.

3.) How does a MAF sensor function?

Most MAF sensors operate on the hot wire concept and are installed in the intake pipe between the air filter housing and the intake manifold. In a nutshell, a MAF has two sensor wires. The first is heated by an electrical current, while the second is not. The heated wire cools as air travels across it. When the temperature differential between the two sensing wires varies, the MAF sensor adjusts the current to the heated wire automatically to compensate. The current is then converted to a frequency or a voltage and transferred to the ECU, where it is read as air flow. The amount of air that enters the engine is changed accordingly.

3.) 2 Common Types of Mass Airflow Sensor

1.) Vane Meter Airflow Sensor

A vane type mass air flow sensor (MAF) measures the amount of air passing through the engine air intake with a metering vane placed in the air stream. This signal voltage is used by the engine control unit (ECU) to calculate the amount of air flowing into the combustion chambers. Signal type: Amplitude varying Type: Mass Air Flow (MAF), vane Signal level: 1.2 V to 4.9 V.

Vane Airflow Sensor

There are some disadvantages to using a vane meter Airflow Sensor:
  • It reduces airflow, which in turn reduces engine output.
  • Its electrical or mechanical contacts that move can wear out.
  • Finding a suitable mounting place in a tight engine compartment is a difficult task to undertake.
  • The vane must be oriented in relation to the center of gravity.
  • In some cases, the fuel pump control was also included in the VAF internal wiring by the manufacturer.

2.) Hot Wire Airflow Sensor

The mass of air flowing into the engine’s air intake system is determined using a hot wire mass airflow sensor. The hot wire mass airflow sensor operates on the same principles as the hot wire anemometer (which determines air velocity). This is accomplished by providing a continuous voltage to a wire hung in the engine’s air stream, similar to a toaster wire. According to Ohm’s law, the electrical resistance of a wire increases as its temperature rises, causing the electrical current flowing through the circuit to vary. Because the supply voltage is constant, as air travels through the wire, it cools, lowering its resistance and allowing more current to flow through the circuit. As more current passes through the wire, the temperature rises until the resistance returns to equilibrium. The rise or decrease in current is proportional to the mass of air passing through the wire. The proportional measurement is converted by the integrated electronic circuit into a proportional voltage, which is then transmitted to the ECU.

Hot wire sensor

The following are some of the advantages of a hot-wire MAF over an earlier design vane meter:
  • reacts to changes in air flow very quickly
  • low obstruction of airflow
  • whole package is smaller
  • mounting location and orientation are less important
  • Its durability is enhanced by the absence of moving parts.
  • cost-effective
  • Even though the intake air temperature sensor is still sometimes incorporated inside the MAF system, separate temperature and pressure sensors are not necessary to estimate air mass.
There are various disadvantages:
  • Dirt and oil might taint the hot-wire, causing it to lose precision.
  • A laminar flow across the hot-wire is required for installation.
  • The sensor comprises a thin platinum wire that, if handled wrong, can break.


Visual, circuit, and component inspections are performed to determine the condition of the MAF sensor. The MAF sensor path must be clean of dirt in order for it to function correctly. If the channel is clogged, the engine will typically start but will run badly or stall, and a diagnostic trouble code (DTC) will displayed.

To troubleshoot a MAF sensor, follow these steps:

During MAF sensor troubleshooting, the following procedures should be followed:

• Inspect the connection for proper fit and good contact.

• Inspect the MAF sensor for wear and tear.

• Inspect the measurement components for wear and tear.

• Test the voltage supply when the ignition is turned on (circuit diagram for pin assignment is necessary). 7.5-14V is the ref. value.

• While the engine is operating, measure the output voltage (circuit diagram for pin assignment is necessary). 0-5V is the reference voltage.

• Inspect the transmission wires between the removed control unit connector and the sensor connector (circuit diagram for pin assignment necessary). The reference value is about 0 ohm.

• Use the engine management control unit to perform an electronic test on the MAF sensor. If a problem occurs, a fault code is recorded in the control unit and may be retrieved with the help of a diagnostics unit.

Testing MAF sensor using Multi Tester

Testing MAF sensor using tester

5.) MAF Mass Airflow Sensor Location

MAF sensors, which are positioned between the air filter and the throttle body, measure the amount of air entering the engine.



6.) What causes MAF sensors to fail?

They have a lot of air moving through them since the MAF sensor is in charge of monitoring air flow into the engine. In fact, for every liter of fuel used, more than 9000 liters of air can travel through the engine. That’s a lot of oxygen! As a result, there is a high risk of contamination. Dust, dirt, and other debris can all get inside the sensor and are a leading cause of MAF failure.

Depending on the vehicle model, contamination could develop as early as 18,000-25,000 kilometers. On small or compact cars, for example, the MAF sensor can clog faster because it is located in a smaller engine compartment that is more vulnerable in vital locations (oil vapor flows and combustion debris). A replacement becomes the equivalent of a long drain oil service in this situation… it almost becomes a service-style repair.

Other typical failure issues are:

• An electrical connection contact problem;

• Defective measuring elements;

• Mechanical damage (accidents, vibrations)

• Element drift measurement (exceeding the measuring framework).

7.) When the MAF (Mass Airflow Sensor) fails

When there is an issue with the mass air flow sensor, the “check engine” or “service engine soon” light on the vehicle’s instrument panel will often come on and glow. When the engine computer detects a problem in one of the components of the emission control system, these lights will illuminate on the dashboard.

6 Common  symptoms When MAF Mass Airflow Sensor Fail:

  1. Check engine light: A malfunction with the MAF sensor, like other engine management components, often causes the check engine light to illuminate.
  2. When an engine runs rich at idle or low under load, it is usually due to a polluted hot wire.
  3. Engine runs rich or lean: this is caused by the MAF constantly misreporting airflow into the engine – a diagnostic procedure will be needed to validate this.
  4. Rough idle or stalls: A failed MAF sensor will not transmit any airflow information to the ECU, preventing it from regulating fuel correctly.
  5. When stationary, there are excessive vibrations.
  6. Without driver input, RPMs change significantly.

8.) How do you repair a damaged MAF sensor?

Once you’ve determined that the MAF sensor is malfunctioning, do the following easy steps:

  • To begin, connect your car to a diagnostic instrument. Choose the proper make, model, year, and engine code for the car you’re working on. Keep track of the failure codes and the MAF sensor’s live data characteristics. After that, quit the diagnostic program and turn off the ignition.
  • You should also inspect the feeds, ground, and wiring. Attach the oscilloscope. A break out lead should be used ideally to avoid puncturing the wire’s insulation and creating a future wiring problem. To obtain a reading, open the throttle and look at the pattern.
  • You’ll need to repair the MAF sensor after it’s been confirmed that it’s faulty. Remove the connection first, followed by the attaching screws. After that, take the sensor out of its housing.
  • Inspect the flow tube to verify that the plastic casing is free of fractures. If there are any, you must replace the whole device, not just the probe. If the flow tube is clear of cracks, you may simply replace the sensor probe.
  • Keep in mind that only the sensor connection should be handled. Never touch the circuitry as this may cause the sensor probe to be damaged.
  • Insert the replacement sensor probe carefully into the flow tube, then tighten the screws and reinstall the connection.
  • Reconnect the diagnostic kit and erase any fault codes that may have been stored (s). Restart the engine and look for any new trouble codes. Exit the diagnostic program and turn off the engine. Finally, ensure that the check engine light has been turned off before doing a road test.

9.) 5 DTC OBD Codes Related to MAF Sensor Problem

  1. P0100 Mass or Volume Air Flow Circuit Malfunction
  2. P0104 Mass or Volume Air Flow Circuit Intermittent
  3. P0103 Mass or Volume Air Flow Circuit High Input
  4. P0102 Mass or Volume Air Flow Circuit Low Input
  5. P0101 Mass or Volume Air Flow Circuit Range/Performance Problem

10.) How do I reset my mass airflow sensor Trouble Code?

  1. Start engine and warm it up to normal operating temperature.
  2. Turn ignition switch OFF.
  3. Disconnect mass air flow sensor harness connector.
  4. Restart engine and let it idle for at least 5 seconds.
  5. Stop engine and reconnect mass air flow sensor harness connector.
  6. Plug the OBD Diagnostic Scanner, Make sure DTC P0102 is displayed.
  7. Erase the DTC memory.

Thank you very much! This tutorial is compile and research by: Erwin Salarda