Mass Air Flow Sensor: All That You Need To Know

Car sensors are essential components in a vehicle. They help regulate certain functions or detect problems with different systems. They are like receptors. The mass airflow sensor is a critical part of the internal combustion engine.

Its primary role is to detect the air mass flow rate getting into the engine. The information helps the engine control unit to determine the fuel level supplied to the engine. It works effectively with an oxygen sensor for improved accuracy.

Looking at the significance of this car sensor, it is not surprising that many people want to know how it works. If you have the same concern, you are in the right place as we look at its working principle and signs of a bad mass airflow sensor.

Mass Airflow Sensor Working Principle

A look at the mass airflow sensor diagram will give you a slight hint of its working principle. Something that you should know is that there are two common types of mass airflow sensors. There is the vane type and hot wire mass airflow sensor. Each of them works in different ways to send signals to the car’s computer unit.

Where is the mass airflow sensor located? You will find this sensor located between the engine’s air filter and intake manifold in most vehicles. In this position, it is on the pathway of incoming air that goes to the combustion chamber.

mass air flow sensor problems

Vane Mass Airflow Sensor Working Principle

Back to the working principle, we will start with the vane mass airflow sensor. It uses a spring that holds a vane located in the air stream and connected to a potentiometer. Incoming air will force the vane to rotate against the spring’s pressure.

As the vane moves, the potentiometer’s slider pushes along the carbon track; one end of the carbon track connects to the power supply unit. The slider movement causes a signal movement change, depending on the vane’s motion intensity. The voltage signal goes to the engine control unit, which will determine the airflow rate. Using the values, it will determine the amount of fuel that will go to the combustion chamber.

Working Principle of the Hot Wire Mass Airflow Sensor

This type of sensor is prominent in most modern vehicles. It relies on the principle of constant temperature. This sensor has a wire exposed to the air path. It is an electrically heated wire made of platinum and other materials of a similar conduction level. Proximal to this wire is a temperature sensor that measures air temperature near the wire.

To understand its working principle, picture the vehicle running on idle. There is little airflow around the wire; as such, it needs a low electric current to heat it. On pressing the gas, the throttle opens, allowing more air into the intake manifold. The more the air intake, the cooler the temperature will be near the wire.

In this case, the power source will provide more current to heat the wire. The air sensor takes note of the current changes and sends the information to the engine computer in the form of digital signals. The computer interprets the info and determines the fuel amount needed for combustion.

Mass Airflow Sensor Problems

Like other car parts, you may encounter problems with the mass airflow sensor. There are telltale signs that will indicate that this sensor is malfunctioning, which we will look at later on in this article. The problems will mostly come due to its wear.

This sensor’s location on the engine’s air pathway makes it prone to agents like dust and other contaminants. These agents contribute to its fast degradation. The contamination may occur from 20000-25000 miles of service, though it depends on many factors.

Among the factors is the car model. In this case, smaller cars with smaller engines are prone to contamination due to short airways. The driving environment is another determinant. If you drive in dusty environments, the mass air sensor will degrade at a fast rate.

Faults at electrical connections may also cause the mass airflow sensor to malfunction. It has electrical links to the power source, and any issue with the connections may bring some problems.

Mechanical damages from heavy impact or vibration can lead to this sensor’s problems. You can notice the issues after an accident or if you drive on rugged terrain. Damaged measuring elements, like the vane or wire, are other causes of this car part’s problems. Worn-out elements can lead to a drift, where the signals are past the measuring bracket.

Can you drive with a bad mass airflow sensor? Well, you can drive with a bad mass airflow sensor, but you will risk fuel economy and a smooth driving experience. A lousy sensor gives inaccurate information to the engine’s computer, and it may interfere with several functions. Some of the engine problems that can come your way include poor acceleration. Also, if you notice that the vehicle will not start on the ignition, you may want to check this car sensor.

Why would a car run better with the mass airflow sensor unplugged? If you notice that your vehicle runs well with the MAF sensor unplugged, it may indicate a problem. It may be relaying the wrong info on air density or temperature. Another likely issue is that you have contaminated wires if you are using the hot wire type.

Additionally, malfunctioning supporting parts can affect the MAF sensor. For instance, if you have bad temperature sensors, the entire unit may break down as it won’t present accurate readings.

Mass Air Flow Sensor

Symptoms of a Bad Mass Airflow Sensor

How do you know if you have a faulty mass airflow sensor? The following are some of the symptoms that may indicate that this engine component is failing.

Engine Throws A Code

A common sign of a failing mass airflow sensor is when the engine throws a code via the check engine light. When the check engine light goes on, it indicates that there is a problem requiring your attention. You can use an onboard diagnostics scanner to read the code from the engine control unit.

In the case of the MAF sensor, the code will be between P0100 to P0199. These codes indicate an issue with the fuel and air metering system. The affected part may be the mass airflow sensor or throttle body.

The most common codes that you will see if you have a problem with this sensor are P0101 and P0102. The former code indicates that it is out of range or a general performance hitch. The latter code comes due to the sensor having a low voltage output. The underlying problem may be a clog due to the presence of foreign objects in the airway.

Stalling And Struggling To Get Power

If the engine is prone to stalling and struggling to get power, you may be having an issue with the sensor. The issue at hand is that the engine is getting more air than fuel, leading to an improper air: fuel ratio. This situation mostly comes due to dirt building up on the sensor’s wires.

Poor Fuel Economy

The prominent role of the MAF sensor is to detect the airflow to the combustion chamber for the release of sufficient fuel. If this part fails or stalls, it may send the wrong information to the ECU. Incorrect signals may lead to excess fuel release, and you may find yourself visiting the filling station more frequently.

Excess Exhaust Fumes

Another sign of a bad mass airflow sensor is the release of excess exhaust fumes. This comes from an incorrect air-fuel mixture, primarily due to the ECU receiving wrong signals from the sensor. Black smoke from the exhaust means the vehicle uses too much fuel, possibly from the disproportionate air: fuel mixture in the combustion chamber.

Additionally, you may notice a strong smell of fuel in the exhaust fumes.

Other symptoms of a poor MAF sensor are poor acceleration, engine knocking, and a rough idle. All come due to an imbalance of the air and fuel mixture.

Mass Airflow Sensor Locations- Depending On Vehicle Model and Brand

As a car owner or mechanic, you must know the location of the mass airflow sensor. As previously mentioned, you find this component between the air intake filter and the throttle body or intake manifold in most car models. It lies on the air pathway for it to detect air density and temperature.

You will realize that this part’s location varies depending on the vehicle model. For instance, you will find that the mass airflow sensor BMW position is on the driver’s side. In this case, if you have a right-hand drive car, the sensor is on the right-hand side. The same applies to a left-hand drive vehicle, where you get it on the left part of the engine.

For GM brands, like Chevrolet, the MAF sensor’s location is precise. It should be at least 10-inches from the throttle body. Its side closest to the filter and throttle body should be at least 3 and 1-inches, respectively, of straight.

Furthermore, you should mount it atop the intake tube at a 180-degree angle. The specifications make it more efficient and less prone to failure. The distance from the throttle body does away with impulses, which may affect the readings.

How to Test Mass Airflow Sensor

If you want to check on the mass airflow sensor’s working condition, you must test it. There are several diagnostic measures to try to check on this component’s functionality. Highlighted below are some of them.

How to Test the Mass Airflow Sensor without a Multimeter

A multimeter is a device that measures values like the voltage, resistance, and current. It is a must-have gadget in your tools box. However, if you do not have it, there is no need to worry as there are ways to check on the mass airflow sensor’s condition without it.

If you have idling problems, start by engaging the parking brake and set the transmission to park or neutral. You then need to start the engine and leave it on idle and pop up the hood. Using an instrument like a screwdriver, lightly tap the mass airflow sensor. Sudden engine stop on running or a change in idling behavior indicates that the sensor has a problem.

If the engine has problems starting, try unplugging the MAF sensor and engage the handbrake, and set the transmission to park. Start the engine. If the engine starts well or the idle improves, it means you have a faulty sensor that needs replacement.

Testing the Mass Airflow Sensor with a Multimeter

If you want more accurate results, you use the digital multimeter. An excellent thing about this gadget is that you can use it to check for various variables. You can start by checking its voltage. Here, the ignition should be off. You then back probe the meter’s red lead to the multimeter’s + wire and the black lead to the ground wire.

Engage the handbrake with the transmission set on parking. Now, start the engine and leave it on idle. On starting the engine, the reading should be around 0.5 to 0.7-volts. Gently tap the sensor using a screwdriver’s handle or a tool at your disposal. If the readings remain steady, then the sensor is in excellent condition. Fluctuations are indicative of bad electrical connections.

You can try revving the engine to increase its speed to a range of 2500-3000-revolutions per minute. If the sensor is in good condition, the multimeter’s signal will have an average rise of 2.0 to 2.5-volts. If there is no voltage increase, you have a faulty car sensor.

Testing the Hot Wire

Still, on testing the mass airflow sensor, you can focus on the hot wire. Check on this wire’s condition as sometimes the issue is you have a broken hot wire. Turn off the ignition and proceed to test the MAF sensor unplugged.

The multimeter should be on the Ohms scale before you connect the meter leads. An infinite resistance is a sign of a broken hot wire.

How to Clean Mass Airflow Sensor

Most of the time, the mass airflow sensor’s problems are due to dirt accumulation. The good news is that there is a solution in the form of cleaning it. To clean this engine add-on, you do not need complex mechanics tools. A screwdriver will do a perfect job in detaching the sensor.

Start by turning the engine off and give it ample time to cool before unplugging the sensor. Place the part on a towel or a layer of newspapers to clean it. You need a cleaner to restore it to a great shape. TheCRC 05110 MAF sensor cleaner is a great option that will enhance horsepower and fuel economy.

Focus on the housing, sides, and connectors to have the sensor in an excellent shape. The cleaning agent should not touch the hot wire. You can cover the wire with tape for your convenience. Let the sensor dry and reattach it.

 You can substitute the cleaner with alcohol. On how to clean a mass air flow sensor with alcohol, you follow the same steps to using a cleaner. You need a spray bottle that you will fill with the cleaning alcohol. Cover the wires and plate, then give a generous spray to this component. Allow for ample time, around an hour, for the MAF sensor to dry before fixing it back.

Can I clean the mass airflow sensor with a carb cleaner? The carburetor cleaner is a very versatile cleaning agent that you can use for many engine parts. However, do not use it on the mass airflow sensor. It has some strong chemical agents that can damage fragile parts of this sensor.

Mass Airflow Sensor Replacement

At times, to do away with mass airflow problems, replacement is the viable solution. You have to get another sensor to fit into your engine as you discard the old one. It is advisable to replace this sensor after serving you for a maximum mileage of 30000-miles. At this point, the sensor may be in poor condition due to the influence of dust and other fumes.

You should also get a replacement if you encounter signs of wear like poor fuel economy and stalling. Testing the MAF sensor shows you its current state, and if on the poor side, get a new one.

Replacing this part is straightforward, especially if you have a background in mechanical works. You will need tools like a pair of pliers and a screwdriver to pull off this procedure successfully. Open the hood and locate the sensor, then remove it.

When removing it, you have to be careful not to cause damage to surrounding parts. Release the binding clip and unfasten the clamp to release the sensor. Carefully lift the sensor from the engine and place it in a safe place. Be keen not to lose the screws and bolts.

Once removed, compare the old sensor to its replacement to be sure to have the correct part. Do away with the dust caps before fixing the new sensor. Now reinstall the new part while being extra careful of some features, like the hot wire.

Fix the screws and clips and ascertain that you have a firm grip. After successful installation, you can use the onboard diagnostics scanner to check for any error codes. If there are no codes, you are good to start the engine and put the new part to use.

How much does the mass airflow sensor replacement cost? The replacement cost of this part ranges from $50 to $350, exclusive of labor costs. The standard MAF sensor’s price is on the lower side of the range, while the most advanced ones are costlier.

If you do not know how to install a mass airflow sensor, you may part with an extra $20 to $60 for labor.


Can You Drive With A Bad Mass Airflow Sensor?

The mass airflow sensor can go bad after prolonged use, mainly if exposed to agents like dust and mechanical damage. Driving your car with a bad sensor is possible, though the drive might be pretty uncomfortable. The vehicle may stall, have a rough idling, poor fuel economy, and general poor engine performance. If you continue driving it in this state, you may cause further damage.

How Much Does It Cost To Replace A Mass Airflow Sensor?

There are times that the MAF sensor is so badly off that the only solution is a replacement. Among the factors to consider are compatibility and price. The latter is essential, mainly when you are working on a budget. The average cost for replacing this engine component is around $150 to $200, without labor. With labor, you will part with roughly $40.

Can A Dirty Mass Airflow Sensor Cause Misfire?

An engine misfire comes about due to incomplete combustion in the cylinders. One of the reasons is an incorrect air-fuel mixture. This disproportionate mixture may come about due to the ECU receiving the wrong signals from the mass airflow sensor. A dirty sensor will malfunction and send incorrect info to the engine control unit. To beat this problem, you have to clean this part regularly.

What Happens If I Unplug The MAF Sensor?

The MAF sensor is essential to the engine when it comes to fuel regulation. Despite its significance, you can still drive your car if you unplug it. The vehicle’s performance will significantly improve if the sensor was bad.

Can I Use Wd40 On MAF Sensor?

WD40 is the to-go cleaning agent for most vehicle parts, upholding its versatility. An exception to its diverse functionality is on the MAF sensor. You should not use it on this engine part as it may leave deposits, further contributing to its degradation. A mass airflow sensor cleaner is the best option when maintaining this element.

How Often Does A Mass Airflow Sensor Need To Be Replaced?

Replacement is a crucial maintenance practice that will boost your vehicle’s efficiency. The MAF sensor needs replacement every 20000-25000-miles. At this point, it is much degraded and not able to work to its best, more so if you drive in rugged terrain. Getting a replacement will help the engine beat issues like knocking and poor fuel economy.

Final Word

Car sensors are like our body’s sensory organs, helping to detect problems and regulate variables like fuel consumption and emissions. In this article, we touch on the mass airflow sensor. It is very significant in the internal combustion engine, where it plays a role in regulating fuel consumption. If you are an automotive engineering enthusiast, this piece is a great asset, showing you how this sensor works. Follow it to the latter to have an upper edge should your vehicle’s MAF sensor fail.


Hi there, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked as a Mechanic and Mechanic Supervisor for over fifteen years at Global Rebound Automotive companies - Toyota, TATA, BMW, Nissan, TVs, and Others. Now, I enjoy my new role of leading a team of automotive experts (in their respective fields) and publish new content on a regular basis on my website and social media.

One thought on “Mass Air Flow Sensor: All That You Need To Know

  1. Thank you Tito for the information about sensors. I am James Kagwe from Kenya and a mechanic in training. I train informally from the streets. I learn from already experienced mechanics.
    I am planning to own a garage specifically for subaru foresters. Its a challenge because without proper tools, there are certain mechanical issues we cannot solve. I am therefore humbly asking if there is any support we can get from your side. I am not asking much….if we could get tools, we dont mind old ones. This will will build our capacity and achieve our goals. I hope this finds you well. Best regards

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