Mass air flow sensor signs of malfunction, reasons, how to check

The main signs of a malfunction of the mass air flow sensor (another name is a flow meter, mass air flow sensor, MAF-sensor) - increased fuel consumption, interruptions in engine operation (loss of power, floating speed, stalls at idle, hard to start when cold) and other similar symptoms of a malfunction Therefore, this sensor is also checked in parallel.

To find out exactly what the reason is, a comprehensive diagnosis of the car is carried out using a scanner (tester) or a random check of sensors, including a flow meter, a multimeter (voltmeter) and other methods. We will discuss these and other points further.

What is he responsible for?

The MAF sensor plays an important role in forming the correct air-fuel mixture. The sensor constantly monitors the volume of air passing through the intake system and transmits the received data to the ECU.

The latter, having received information from the flow meter and other sensors, forms a fuel-air mixture that guarantees engine operation at optimal speeds with minimal fuel consumption.

Other sensors can also correct the MAF readings: atmospheric pressure and air temperature, but they are not installed on all cars.

If the MAF sensor is broken, then the volume of incoming air is determined by the controller based on the angle of the throttle valve. This does not ensure economical operation of the engine, but the car drives.

Why do you need a mass air flow sensor

The power plants of new cars are equipped with a “smart” fuel supply system. Electronic units monitor device parameters in real time and allow you to accurately calculate the required amount of fuel and air.

The mass air flow sensor plays an important role and if it fails, the control system begins to work incorrectly. The internal combustion engine begins to choke or choke, which negatively affects its performance and power.

The air flow sensor itself transmits information to the computer about the amount of gases entering through the intake manifold, which allows it to correctly determine the required volume of fuel to form a mixture.

Types and principle of operation of flow meters

The mass air flow sensor is a hot-wire device.

The main types that are used on cars:

1. Film with analog and digital signal.
2. Wire (thread) analog.
3. Frequency mass air flow sensor. Already installed on most modern cars coming off the assembly line.

Pitot tube (vane type) flowmeters are not considered due to their outdated design.

The operating principle of the first two types of devices is similar to each other and is based on changing the voltage readings supplied to the heating elements (threads or film). The ECU monitors these changes and performs calculations to form the fuel-air mixture. More details below.

Wire mass air flow sensor

Used on most modern cars. In such devices, the key role is played by thermistors - two tungsten or platinum filaments with a diameter of 0.07 mm, to which voltage is applied with a certain current strength, as a result they heat up, as well as a thermistor (temperature sensor), but it is not provided everywhere.

One thread is closed from the air flow, and the second, with the throttle valve open, on the contrary, is blown and actively cooled.

To equalize the temperature readings of thermistors, more current is supplied to the open thread.

The ECU takes into account the difference in voltage readings between the threads, the intensity of their cooling and, based on them, calculates the volume of incoming air and, in accordance with this, calculates the required amount of fuel supplied to the cylinders.

Wire mass air flow sensors have several significant disadvantages: over time they become dirty or wear out.

To solve the first problem, the designers developed a self-cleaning mode. It provides for short-term (so as not to discharge the battery) heating of the filament to 1000-11000C with the engine turned off. At this temperature, all deposits burn out.

When the thermistors wear out, the sensor is replaced.

Film flowmeters

Structurally, such sensors differ from the first ones, although the principle of their operation is largely the same.

Instead of a sensitive thread thermistor, a platinum-coated ceramic heating element or semiconductor film is installed here.

The location of the film device remains the same, and the ceramic element itself has several resistor layers, each of which performs its own function: a temperature sensor, a heating one, two thermistors.

An important advantage of such a sensor is that it measures the temperature of not only the incoming air, but also the reflecting air. The device is also less susceptible to contamination.

It is worth noting that in modern devices, the output signal U is transmitted not only in analog mode, but also in digital mode, this speeds up data processing.

Frequency mass air flow sensor

The General Motors product was installed on the first VAZ 2109 and worked in tandem with the January 4 ECU. It is characterized by reliability and a long service life.

The principle of operation is not based on a change in direct voltage, but on a change in the frequency of the output signal of an alternating signal U. When the frequency is high, this indicates high air flow, low frequency indicates low air flow.

The main advantage of a frequency flow meter is stable data transmission to the ECU when the voltage in the circuit drops (poor contact, oxidation, etc.).

Let's imagine that the contacts in the connectors have oxidized. Then the output signal of 1.02V will decrease and, for example, 0.9V will come to the controller. This is not critical, but it will increase fuel consumption.

In the frequency sensor, voltage surges do not affect the operation of the ECU in any way. Oxidation of the contacts will not change the signal frequency in any way, which means 100% of the output data will reach the recipient, i.e. controller (ECU).

Functionality check

Before diagnosing the mass air flow sensor, you need to know the symptoms that allow you to determine the degree of performance of the MAF (abbreviation for the English name of the device) sensor in the car. We list the main symptoms of a malfunction:

• The consumption of the fuel mixture has increased significantly, while at the same time acceleration has slowed down.
• The internal combustion engine idles with jerks. In this case, a decrease or increase in speed may be observed in idle mode.
• The engine does not start. Actually, this reason in itself does not mean that the flow meter in the car is faulty; there may be other reasons.
• A message appears about a problem with the engine (Cheeck Engine)

An example of the displayed message “Cheeck Engine” (marked in green)
These signs indicate a possible malfunction of the mass air flow sensor; in order to accurately determine the cause of the failure, it is necessary to perform diagnostics. It's easy to do it yourself. Connecting a diagnostic adapter to the ECU (if this option is possible) will help to significantly simplify the task, and then determine the serviceability or malfunction of the sensor using the error code. For example, error p0100 indicates a fault in the flow meter circuit.

Finding an error using a diagnostic adapter

But if you need to carry out diagnostics on domestic cars manufactured 10 years ago or more, then checking the mass air flow sensor can be carried out in one of the following ways:

1. Testing while moving.
2. Diagnostics using a multimeter or tester.
3. External inspection of the sensor.
4. Installation of a similar, known-good device.

Let's consider each of the listed methods.

Testing while driving

The easiest way to check is by analyzing the behavior of the internal combustion engine with the MAF sensor disabled. The algorithm of actions is as follows:

• You need to open the hood, turn off the flow meter, close the hood.
• We start the car, and the internal combustion engine goes into emergency mode. Accordingly, a message indicating a problem with the engine will appear on the dashboard (see Fig. 10). The amount of fuel mixture supplied will depend on the position of the remote control.
• Check the dynamics of the car and compare it with what it was before the sensor was turned off. If the car has become more dynamic and power has also increased, then this most likely indicates that the mass air flow sensor is faulty.

Note that you can continue driving with the device turned off, but this is highly not recommended. Firstly, the consumption of the fuel mixture increases, and secondly, the lack of control over the oxygen regulator leads to increased pollution.

Diagnostics using a multimeter or tester

Signs of a malfunction of the mass air flow sensor can be identified by connecting the black probe to ground, and the red probe to the sensor signal input (the pinout can be found in the device data sheet, the main parameters are also indicated there).

An example of measuring the voltage on the mass air flow sensor in a VAZ 2114 car with a multimeter

Next, we set the measurement limits to 2.0 V, turn on the ignition and take measurements. If the device does not display anything, you need to check that the probes are connected correctly to ground and the flow meter signal. Based on the readings of the device, you can judge the general condition of the device:

• A voltage of 0.99-1.01 V indicates that the sensor is new and working properly.
• 1.01-1.02 V - used device, but its condition is good.
• 1.02-1.03 V - indicates that the device is still operational.
• 1.03 -1.04 the condition is approaching critical, that is, in the near future it is necessary to replace the mass air flow sensor with a new sensor.
• 1.04-1.05 – the device’s resources are almost exhausted.
• Over 1.05 - a new mass air flow sensor is definitely needed.

That is, you can correctly judge the state of the sensor by the voltage; a low signal level indicates an operational state.

External inspection of the sensor

This diagnostic method is no less effective than the previous ones. All that is necessary is to remove the sensor and assess its condition.

Inspect the sensor for damage and fluid

Characteristic signs of a malfunction are mechanical damage and liquid in the device. The latter indicates that the oil supply system to the engine is not adjusted. If the sensor is very dirty, the air filter should be replaced or cleaned.

Installing a similar, known-good device

This method almost always gives a clear answer to the question of the sensor’s performance. This method is quite difficult to implement in practice without purchasing a new device.

What does the malfunction lead to?

It cannot be said that a breakdown of the flow meter will immediately lead to critical consequences, but if you ignore the problem, then prolonged operation of the engine on an incorrectly formed air-fuel mixture will lead to rapid wear of the elements of the cylinder-piston group, and when several factors overlap, detonation in the engine and even its “wedge” can occur. .

For example, if a rich mixture enters the engine, the engine will quickly overheat as a result of oil dilution.

Also, a faulty MAF sensor, due to deterioration in exhaust purity, significantly affects the reduction of the service life of the catalytic converter, particulate filter and exhaust system as a whole.

Functions and purpose of the sensor

Nowadays, cars use two types of fuel supply: with distributed injection, fuel is supplied to the inlet pipe, and with direct injection, fuel is supplied directly into the chamber. In both situations, the operation of the vehicle depends on the correct functionality of the mass air flow sensor. Several years ago it worked on a mechanical basis, but now there are no moving elements and the sensor is manufactured on a hot-wire type.

The mass air flow sensor is suitable for any type of engine, and the functionality of the valve of the exhaust gas removal and neutralization complex is concentrated on it.

As experienced drivers like to say, the engine does not function in only two ways - there is nothing to burn or nothing to ignite.

Using an air flow sensor, the control unit receives information about the volume of gases entering through the intake channel, which regulates the required amount of fuel to produce the mixture.

Signs of malfunction of the DMVR

As is already clear from the above material, if the mass air flow sensor is faulty, the ECU forms a fuel-air mixture without maintaining the correct proportion.

For example, you need 1:14, and the mixture will enter the cylinders in a ratio of 1:15 (lean) or 1:13 (rich). And at a ratio of 1:5 the mixture does not ignite at all.

As a result, a breakdown of the flow meter may manifest itself with the following symptoms:

1. Difficulty starting the engine (especially in cold weather).
2. Increased fuel consumption.
3. Floating speed at idle, the car stalls. At the same time, this may not happen on a cold engine, but as soon as the engine warms up, the speed jumps from 1000 to 1600 per minute.
4. The engine does not pull, acceleration dynamics have disappeared.
5. The car drives jerkily.
6. The car stalls when upshifting or downshifting.
7. The "Check Engine" light comes on and does not go out.
8. Rapid overheating of the motor.

It is important to understand that all these signs do not specifically indicate a malfunction of the MAF sensor and here you need to take a comprehensive approach to finding the causes of the failure and use different diagnostic methods.

Causes of failure

Here we list the main reasons why the mass air flow sensor fails or does not work correctly:

1. Burnout (burst) of the thermistor or damage to the coating on the tracks. This disease is especially typical for the HFM-5 sensor model. This can happen as a result of natural wear and tear or a sudden surge in voltage in the network (the generator has failed, etc.). On average, wire devices last about 150 thousand car miles.

2. Lack of voltage – break in the signal or operating electrical circuit, the sensor is not connected, oxidation of the contacts.
3. The ECU has failed.
4. Incorrect maintenance. The flow meter is considered a maintenance-free device and can be replaced as an assembly. But since it is expensive, many try to clean it, for example, with cotton wool, which is wrong. To do this, use compressed air or special liquids (carbocleaner, special air flow sensor cleaner or other alcohol-based product).

Indirect reasons:

1. The throttle valve is jammed as a result of its contamination - in this case, the sensor seems to be working, but the information is not transmitted to the ECU correctly.
2. The air filter is clogged.

If all else fails, buy a new air flow sensor

All testing methods showed the same result - “Sensor to be replaced.” The mass air flow sensor is quite expensive, and you should approach its purchase consciously.

Using the example of the same manufacturer Bosch for LADA and GAZ (article 0280218037) - according to the search results on the GisAuto portal as of September 18, 2022, 568 offers from different cities were found in Russia. The cost of this sensor varies from 2,490 rubles. up to 6,676 rub. Such a range in prices may depend on various reasons: availability, delivery time, purchase cost, etc.

You can select a mass air flow sensor for your car on the GisAuto portal - you can use the part number, make and model of your car, and also create a request using the VIN number of the car, and then the sellers themselves will send you their offers. All you have to do is choose the option that suits the price and time frame.

How to quickly determine that the sensor is faulty?

To quickly check the mass air flow sensor for functionality, do the following:

1. Start the car and warm up the engine to operating temperature (up to 80 degrees is possible). To speed up the process, increase the speed periodically.
2. Turn off the car.
3. Disconnect the terminal from the sensor.
4. Start again without pressing the gas pedal.
5. If the engine begins to sharply gain speed, which is not typical for idling, then, on the contrary, goes to the bottom, then the air flow meter is faulty.

VAZ 2110 air sensor pinout diagram

1. Yellow (closest to the windshield) - mass air flow sensor signal input;
2. Gray-white—sensor supply voltage output;
3. Green — sensor grounding output;
4. Pink-black - to the main relay.

The wire colors may change, but the pin locations remain the same.

Let’s also add that the mass air flow sensor with endings 004, 037, 116 (for Bosch) and 00, 10, 20 (for Pekar) are different in calibration. You can only change it by flashing it.

How to check frequency-type air flow sensor

Let's look at the example of Citroen Peugeot 1.6 HDI diesel. A similar four-wire MAF sensor is found on the models shown below.

To check, you will need a diagnostic scanner or multimeter that supports this function.

Sensor pinout:

1. Intake temperature sensor output signal.
2. Weight.
3. Not involved.
4. On-board voltage +12V.
5. Frequency signal from the sensor.

Connect:

• Second Pin – “ground”
• The fifth Pin is the output signal.

At rest with the ignition on, the output frequency should be 5 kHz.

After starting the engine at idle, the frequency should decrease and vary from 1.02 to 3.3 kHz. For each frequency mass air flow sensor frequency table.

Features of testing for Ford Focus 2

In most cases, for foreign cars, the flow meter diagnostic methods are similar, but they still have their own characteristics. It all depends on the car model and the brand of the installed MAF sensor.

For example, on Ford Focus 2 there are sensors with four or six wires. Original product FORD 1072308.

The pinout is shown below using an example of a 4-wire sensor.

• A – voltage 12V.
• B – “–” (mass).
• C – “–” reverse earth (literal translation).
• D – output signal SIG to the ECU.

Two additional wires are connected to the 6-pin sensors: IAT (intake air temperature) sensors.

To check the mass air flow sensor on a Ford Focus 2, do the following:

1. Disconnect the connector from the flow meter.
2. Turn on the ignition.
3. Connect the “–” of the multimeter to “B” (ground) on the wiring harness (see the figure above).
4. “+” of the device to positive “A” (12V).

The multimeter should show 12V. If not, then we look for the reason why the sensor does not receive U.

Next steps (you will need an assistant):

1. Plug the chip back in.
2. Without turning off the ignition, using sharp multimeter probes, connect “+” (pierce the wire) to the signal “D”, and “–” to “C” (reverse ground). The norm is 0.9 – 1.0V.
3. Ask an assistant to start the car, warm it up and set the speed to 1500. The device should show 1.4 - 1.6V. At 2500 rpm – 1.8 – 2.0V.
4. With the gas pedal fully depressed (as the speed increases), the device should show from 0.2 to 5V.

The range of standard indicators is not indicated by chance. It will vary depending on engine size.

Also diagnose Ford Focus 2 with a scanner (read above). The standard air flow rate is 9–12 kg/h or about 2.8 g/s at idle speed.

Why does the mass air flow sensor fail?

The sensor itself is a simple structure installed on the line between the air duct and the throttle.

The sensitive sensor is covered with an impenetrable plastic casing, which protects it from vibrations and moisture and dust. Failure of a device without reason is impossible - its design excludes this. Usually the sensor breaks down due to the following factors.

1. Mechanical damage. If the sensor is not repaired carefully or is involved in an accident, the sensor housing may be damaged, which may cause its failure.
2. Getting wet. Water ingress during improper washing is a common reason for visiting a service station. Also, similar problems can occur when the car is left in the rain with the hood open.
3. Short circuit of the on-board network - with a sharp increase in voltage, delicate electronics can burn out or completely fail.
4. Deep discharge of the battery. Some machines use electronics designed to operate only at normal voltage. If the actual reading falls below the set limit, the equipment may malfunction.
5. Manufacturing defect. No one is immune from manufacturing defects. This is especially true when purchasing non-original parts from dubious manufacturers. Using only branded parts from trusted brands will help you avoid this.
6. Software glitch. Such problems are not a direct failure of the device, but they cause a lot of inconvenience. Motorists often go to service stations with problems with their on-board computer.

In some cases, damage to the accompanying elements may also be responsible for the incorrect behavior of the sensor. For example, on domestically produced cars and old foreign cars, factors that can often provoke such behavior are:

• the sensor terminal connector has become loose;
• the wiring responsible for the sensor is damaged;
• There is oxidation and rust on the contact group of the device;
• Signal wires are incorrectly connected;
• The ECU reads the data incorrectly;
• the corrugated air supply channel is damaged (the wall is cracked and some of the gases escape);
• The fastening clamps are not tightened tightly.
• firmware glitch;
• The air filter is clogged or damaged.

In some cases, the device may fail for a completely unpredictable reason. It happens that this happens right while driving on the road and nothing portends trouble.

Nissan Almera

Nissan Almera is equipped with mass air flow sensors from Hitachi, although you can also find products from Bosch. And you need to understand that the readings on devices from different manufacturers will differ.

To understand the process, we will make replacements on the Hitachi flow meter. Read above for the example of Bosch.

There are 5 wires going to the sensor. Measurements are taken first with the ignition on, then with the engine running. Prepare the multimeter by switching it to 20V mode.

Procedure:

1. Insert a needle or pin into the third wire (pierce the insulation) on the air filter side.
2. Turn on the ignition. “–” of the multimeter for battery ground, “+” for the needle. The norm is no more than 0.4V.

3. Start the car and follow the steps in step 2. The norm is no more than 1.04V. Up to 1.05V is still respectable.

How can you bypass the regulator?

DMRV decoy circuit

If you don’t want to deal with the problem of the flow meter not working, then there is one option for deceiving the control unit. To do this, a diode is installed instead of the mass air flow sensor. In order for the blende to work normally, the engine must be in working condition in any case. If the power unit does not work correctly or there are malfunctions in its operation, then the blende simply will not have an effect.

In order to deceive the “brains”, you will need a diode that will have a drawdown of 0.3 volts; it can be purchased without any problems at any electronics store. The diode element will be used to supply from the reference 5 V to the signal 4.7 V. This will allow the control unit to “think” that the mass air flow sensor sees a fairly large volume of air flow. For example, consider Volkswagen car engines.

If this car uses a regulator from the manufacturer Bosch, then the diode element is installed from pin 4 to pin 5. If a flow meter from Pierburg is used, then the diode is installed from pin 1 to pin 6. The installation of the diode element is carried out taking into account the direction of flow, since it allows the passage only one way.

Flushing the sensor

Flushing the mass fuel flow sensor is a slippery topic. This helped some, while others, on the contrary, remained stuck with the “broken trough” - the flow meter completely failed.

The process itself is not complicated, disassemble (if the design allows) and clean the threads or film. If it is not possible to disassemble, use compressed air.

To wash the air flow sensor, special alcohol-based products are used.

Carburetor cleaners, solvents, and gasoline are used at your own risk. For some, the problem was solved, for others, the platinum coating was washed off.

Do not saw the product point-blank, but from a distance of 5–10 cm.

How to troubleshoot?

There are two ways to get rid of problems in engine operation if they are related to the flow meter - by changing the device or cleaning it.

Replacement

The controller changes like this:

1. The car's ignition is turned off and the hood opens.
2. The block with cables connected to the flow meter is disconnected.
3. The inlet hose that comes from the air filter element is disconnected. To do this, you need to loosen the fixing clamp in advance using a Phillips-head screwdriver, as shown in the photo.
4. Using a 10 mm wrench, unscrew the two screws that secure the flow meter to the housing of the filter device.
5. The controller is being dismantled.
6. The tightness of the sealing element at the location where the flow meter is installed is diagnosed. If the ring is worn out, it is replaced.
7. A new controller is installed and securely fixed to the filter device. The hose is put back onto the flow meter body and the clamp is tightened.

Loosening the clamp on the air flow pipe of the mass flow sensor

Disconnecting the power supply from the flow meter

Removing the device from the seat

Cleaning

The inside of the controller may be covered with traces of oil; when cleaning, you need to get rid of this layer. To accomplish this task, you can use a carburetor cleaner. There is a film inside the flowmeter, on which there are several sensors made in the form of wire. They are fixed to the device using a special resin. You need to take the product and carefully spray it on the sensitive component so as not to spoil it.

Then you need to wait a few minutes until the liquid dries. The cleaning procedure is repeated as many times as necessary to completely remove contaminants. To speed up this process, you can additionally use a compressed air cylinder, which will be used for drying. If there is no carburetor cleaner, other means, for example, alcohol, can be used. In addition to the flowmeter itself, it is necessary to remove dirt from the internal surface, and debris and dirt from the device’s pipe are also removed.

Purchasing a new and replacing the mass air flow sensor

Purchasing and replacing a mass air flow sensor is not a problem. The market is teeming with offers. Prices also vary from 2500 to 9000 rubles. For VAZ and GAZ, look for Bosch products with article number 0280218037.

To replace you will need:

1. Cross-shaped or flat decoction.
2. Key head 10 (for Lada Kalina).

Procedure:

1. Loosen the air duct clamp bolt and move the latter to the side.
2. Press the button under the plug and pull the latter out of the connector.
3. Using a 10mm wrench, unscrew the two bolts (one on top, the other on bottom).
4. Remove the sensor.
5. Installation in reverse order.

1 of 3

— +

1.

2.

3.

Before buying a new flow meter, pay attention to the markings of the old one. It is advisable to purchase a product with the same marking so that it is guaranteed to be compatible with the car’s ECU.

The main thing after replacement is not to forget to adapt the new flow meter. To do this, remove the negative terminal of the battery for a few minutes to expose the data in the ECU.

In some car models, this cannot be done in a garage; you will have to go to a service center where there is special diagnostic equipment.

Recommendations for increasing service life

To extend the life of the MAF sensor, follow these recommendations:

1. Change the air filter promptly to minimize clogging of the flow meter.
2. Monitor the technical condition of the engine, carry out maintenance on time, change and fill only with high-quality engine oil.
3. If the car has a high mileage, check the engine compression - wear or jamming of the piston rings and valve seals will lead to oil penetration into the intake system. This will prevent the appearance of oil deposits on the thermistors.
4. Monitor the condition of the crankcase ventilation system. This is especially true for those engines where the crankcase gas suction pipe is connected in front of the mass air flow sensor. Check the condition of the oil separator under the valve cover.