DMRV for VAZ - restoration of performance. The main symptoms of a malfunction of the DMRV VAZ 2112 DMRV pinout

The video shows the symptoms of a faulty mass air flow sensor on a VAZ. A non-working mass air flow sensor was specially installed:

Signs of malfunction of the DMVR

Mass air flow sensor design

Signs of a malfunctioning mass air flow sensor can be direct or indirect. Let's consider all possible options:

1. . In most cases, the CHECK indicator lights up due to the failure of one of the sensors, so you need to connect to to accurately determine the malfunction.
2. Power drop is only an indirect sign, since there may be another reason for this malfunction.
3. Increased fuel consumption . Of course, everything can be attributed to the fuel pump, but the fuel pressure sensor must also be checked. .
4. Reduced acceleration dynamics . An incorrect amount of air mixture that enters the combustion chambers produces a poor ignition mixture, which in turn does not give and leads to.
5. Poor or inability to start . Rich or cannot detonate normally, which will lead to just such problems. It is also possible that fuel does not burn out and...
6. . Different amounts of air entering the fuel mixture will have an effect when the speed will either decrease or increase.

To accurately determine the malfunction of the DMVR sensor, it is necessary to diagnose it.

How to check the MAF sensor?

The mass air flow sensor is checked using a multimeter

The mass air flow sensor is quite easy to check. For diagnostics you will need a multimeter.

Voltage readings of a working and faulty sensor

• 1.01-1.02 - readings from the new sensor, everything is normal.
• 1.02-1.03 - there is wear, but the parameters are within normal limits.
• 1.03-1.04 - the parameters are working, but there is already wear.
• 1.04-1.05 - critical parameters, get ready for replacement, if you have the money, then we’ll change it. Fuel consumption may be reduced.
• 1.05 and higher- the MAF sensor is not working.

Measurement using paper clips - there may be an error on the device. According to the readings, it is clear that the sensor “ordered to live long”

Alternative verification method

The second way to check the performance of the mass air flow sensor is to disconnect the power from it and drive a few kilometers. If engine performance has improved, then the problem is in the mass air flow sensor.

conclusions

It is quite easy to determine the malfunction of the mass air flow sensor VAZ-2112 16 valves. To do this, you need to know the direct and indirect reasons that contribute to the diagnosis, as well as carry out testing in the most basic ways.

The mass air flow sensor is a mass air flow sensor. It is located in the engine power system, in the intake tract, and is considered the most important among the main instruments and components in the injection system of any power unit. Like any other car component and any part, the mass air flow sensor can fail. Let's look at the main symptoms of a malfunction of the mass air flow sensor, and also find out the principle of operation and functionality of this equipment.

What is a DMRV?

This device is very necessary in order to determine the volume of air that fills the combustion chambers when the engine is running. The sensor is usually installed after the air filter in the power system.

When driving, the automobile power unit is supplied with 1 volume of fuel, as well as 14 equal parts of air. This prepares the correct fuel-air mixture. This is the key to proper operation of the motor in the most optimal modes for it. For any violation of this ratio, the car owner will observe either increased fuel consumption, or a decrease in the power of the power unit, or both. If you know the signs of a malfunction of the mass air flow sensor, it is easy to identify a breakdown of the device.

The mass air flow sensor is necessary in order to accurately measure the required amount of air. This amount is calculated in the sensor itself and then sent to the ECU, where, based on these data, the required amount of fuel will be calculated.

The more the driver presses the accelerator pedal, the more air enters the combustion chambers. The sensor records the amount and sends a special command to the ECU to increase the volume of injected fuel. If the car is to run or drive more smoothly, then a small amount of air will be needed. This is why you need a mass air flow sensor. It measures the required volumes of air for engine operation with maximum accuracy.

Measuring the volume of air means determining the load that will be applied to the motor. When you press the accelerator pedal, the throttle valve opens and the volume of air received increases.

How does the MAF work?

This device is a small wire made of platinum alloy. The size of this cord is only 70 microns. It is installed in a special tube, which is located in front of the throttle valve.

This wire is cooled under the air flow. To regulate the temperature between it and the air flow, electricity is applied to the wire. The charge level can be adjusted. The more the wire is blown, the more electricity is supplied.

Due to constant use, this wire is constantly covered in dirt. But modern sensors have a self-cleaning system. Dirt is one of the reasons why the device fails, but there are other signs of a malfunctioning MAF sensor. Although the design of the device is as simple and reliable as possible, it also fails. Its only drawback is that it is not suitable for repair. If the sensor fails, it is simply replaced with a new one.

MAF VAZ - signs of malfunction and diagnostics

If this sensor fails, the “Check Engine” light will most likely light up on the dashboard.

The motor will also definitely lose its power and dynamic characteristics. Also among the main signs are increased engine appetite and difficulty starting the internal combustion engine.

Methods for diagnosing the air flow sensor

There are several options for checking the mass air flow sensor. Signs of a malfunction will appear almost immediately. Let's look at them together.

The first method is to disable the sensor

This verification method is the simplest. Every car owner can do it. The first step is to turn off the sensor. To do this, you just need to unplug the connector. Then you should start the engine. As a result, the ECU controller will go into emergency mode. And the supply of the fuel mixture will be regulated only using the throttle valve. Idle speed will be around 1500 rpm. After this, you need to check in by car. If the car has improved its dynamic acceleration characteristics, then it makes sense to look for signs of a malfunction of the mass air flow sensor.

The second way is using a multimeter

Before performing these diagnostic steps, it should be noted that this will only work with a Bosch mass air flow sensor. Before performing the test, set the limit on your multimeter to 2 V, and then switch the device to constant voltage operation.

Turn on the ignition and connect the red wire to the yellow one on the block. Connect the black wire to the green one. At this moment the engine should not be running. Measure voltage

If the reading is between 1.01 and 1.02, then everything is fine. The multimeter shows voltage up to 1.03 - there is nothing to worry about, this is acceptable. The limit level is 1.05. If it is higher, then you can again look for the cause of the breakdown.

External signs of a malfunction of the VAZ 2110 mass air flow sensor

This is the third way to diagnose the sensor. To determine its serviceability, carefully inspect the internal cavities of the air pipe where the mass air flow sensor is mounted. In order to do this, you will need a shaped screwdriver. Loosen the clamp and disconnect the corrugated pipe. The surface of the corrugation should be as dry as possible, without an oil film.

It should be noted that the main signs of a malfunction of the mass air flow sensor are dirt on the working surface. It is formed due to the fact that the air filter was not replaced in time. Oil deposits will tell the driver that the oil level in the lubrication system is high or that the oil cutter is not working properly. With these signs, the sensor may still work, but will soon fail.

Next you need to completely remove the mass air flow sensor. You will find signs of a malfunction after a visual inspection of the device. To carry out this operation, you will need a 10mm wrench. Unscrew the two screws and remove the device from the air filter housing. A rubber seal will come out with the sensor. If the seal remains in the body, this is the main sign of imminent failure.

Main symptoms

So. If you have problems with your mass air flow sensor, the signs of a malfunction can be very different. Among them are failures during acceleration, lack of traction, and decreased power. There is a persistent feeling that the car simply “does not go.” If there is no proper response when you press the gas, then this is one of the signs. High fuel consumption is also a signal for diagnosing this sensor. When your car stalls when shifting from gear to gear, it makes sense to check the MAF sensor. The VAZ 2110 has the same symptoms of malfunction as other cars.

If you have difficulty starting a cold engine, if the engine operation is unstable, if the speed spontaneously increases or, conversely, decreases, if detonation occurs under load - these are all signals for checking and diagnosing the sensor.

Cleaning the sensor

If you observe signs of a malfunction of the mass air flow sensor, then you can try cleaning the device.

By the way, this is the most expensive sensor of all in the line of front-wheel drive VAZ cars. But if yours is broken, don’t rush to change it. There is a small chance of restoring his “health”. For the cleaning process you will need a special liquid that is used to clean the carburetor. Star keys are also useful. Unscrew the clamp, as well as the two “10” bolts. Remove the pipe and take out the sensor. Spray the liquid onto the wire and tube. Work with extreme care, wait until this liquid has completely evaporated and leave the device to dry.

While the device is drying, remove the throttle assembly. You will see plaque inside the throttle assembly. It needs to be removed with liquid. This dirt causes problems with the entire system. Because of it, problems with the mass air flow sensor appear, signs of a malfunction of the VAZ 2115, which bother beginners on automobile forums.

Do not remove the throttle cable. Place the knot on a cloth and treat particularly dirty areas with the liquid. Don't forget to clean the idle air control valve and the space underneath it.

After this, most likely, all signs of problems with the mass air flow sensor will go away, of course, provided that the sensor has no mechanical damage. Therefore, do not wait until you have the first signs of such problems, but take such prevention this coming weekend. It won't take you much time, and your car will truly breathe. You won't recognize your engine. It will start much better, its traction will improve, and you will notice an increase in the power of your engine.

Carry out such preventive maintenance regularly, and your car will thank you.

Listening to auto mechanics' diagnostic results and repair forecasts, very often the mass air flow sensor (mass air flow sensor) is mentioned as a possible cause of the malfunction. It is practically beyond repair, and replacement costs a pretty penny. Sometimes, after making a replacement, it turns out that the breakdown has not disappeared and the check signal still cheerfully informs us about problems in the engine system. Therefore, correct diagnosis and correct understanding of the sensor’s operation will save time and money for the car enthusiast.

Mass air flow sensor - what is it, the function of the mass air flow sensor

The only function of an expensive sensor is to measure changes in the force of air flow entering the internal combustion engine. It is a mistake to think that the sensor regulates the air flow. Based on the meter readings, the engine ECU (on-board computer) regulates the flow of fuel, achieving the optimal composition of the fuel-air mixture.

In the latest models of foreign passenger cars, the meter is supplemented with correlating sensors for temperature and atmospheric air pressure. The readings of several sensors help control the ignition timing, increasing engine efficiency.

The mechanism of operation of the flow meter, the design of the mass flow sensor

The operation of common sensor models is based on measuring the electrical power required to maintain a stable temperature of the heated element of the device. In older designs (pitot tube vane flowmeters), a potentiometer measures the degree of blade bending.

The main designs of flow meters are equipped with hot-wire meters with wire, plate, and film elements. When the ignition is turned on, the refractory element of the flow meter heats up, sending the ECU an initial signal. Opening the throttle valve causes additional air flow, cooling the hot-wire anemometer. The sensor measures the electrical voltage required to additionally heat the element. This value becomes a calculation indicator for determining fuel injection. The high price of a wire meter is due to the presence of precious metals (platinum) in the mechanism and the precision assembly accuracy.

The operation of a membrane flow meter is based on similar principles. The signal to the electronic control unit records the temperature difference on the sides of the membrane, since the inner side cools more slowly.

Structurally, the air flow meter consists of a plastic cylindrical pipe, inside of which a hot-wire anemometer meter is mounted. Air is drawn in through a grille deflector (metal or plastic) equipped with rubber O-rings. The electrical circuit connector with power supply wires and signal to the ECU is located on the outside of the device. The device is placed between the air filter and the engine.

Causes of malfunction, signs of failure

The main reasons for the malfunction of the mass air flow sensor are natural wear (combustion) of the wire, meter membrane, and contamination of the hot-wire anemometer. Damage to the device can be caused by extreme modes of vehicle use, long-term operation, and rare air filter replacements. A clogged filter allows oil and resins to pass through to the flow meter, which are deposited as a film on the wire or membrane, distorting the readings.

Signs of a malfunctioning meter include:

1. Changes in engine speed at idle.
2. The “check” signal appears on the on-board computer display.
3. Dips in engine power when using the accelerator.
4. Engine stops while moving.
5. Increased fuel consumption.

Such symptoms cannot be considered an unambiguous indication of a breakdown of the flow meter; similar symptoms occur when the throttle valve, USR valve, fuel pump, or ignition module malfunction. A final answer is only possible by diagnosing the meter.

The ECU responds to failures in the flow meter readings by switching the engine to emergency mode. Based on the readings of the crankshaft and throttle position sensors, the control unit supplies the engine with a supersaturated mixture, worsening power and economic performance.

Self-test of the sensor

To independently check the electrical signals of the flow meter, which is not particularly difficult, you will need a multimeter. The first stage is diagnosing the functionality of the detachable connection (chip). To do this, use the positive probe of the tester to check the red-black connector on the removed chip. By attaching the second probe to the cleaned motor bolt, we compare the voltage readings in the network. If the readings coincide with the battery charge, we can talk about the serviceability of the chip.

The standard pinout of flow meters manufactured by Bosch, used in many VAZ models, uses the following colors (by location from the windshield):

1. Light yellow. Signal input.
2. Grey-white. Sensor power cable.
3. Green. Grounding the flow meter.
4. Pink-black or white. Signal to the ECU.

Having connected the connector to its original place, we check the readings with the engine not running. The mass probe remains in the same place during further tests. By inserting the positive probe into the fourth wire, we get readings of the transmitting signal to the computer. The standard signal voltage of a working flow meter ranges from 1.0 - 1.02 volts. Readings above 1.05 volts indicate the need to replace the sensor.

At idle speed (the engine needs to be warmed up), the standard readings vary from 1.2 to 1.8 volts. To check the efficiency of the mass air flow sensor, we check the readings by opening the throttle valve several times. An increase in engine speed should cause an increase in signal strength.

Maintainability of the device

Vane sensors are considered conditionally repairable, although almost all auto mechanics refuse to repair them. Real repair of the flow meter comes down to replacing the device assembly. The operations of dismantling and installing the device are simple; the cost of replacement is increased by the need for several types of diagnostics and checking other components that cause identical engine behavior. The selection of a replacement sensor should be trusted by an experienced auto mechanic who knows the features of your car model.

To buy a replacement sensor you will need to spend 4,000 - 9,000 rubles (depending on the design of the meter and the car model). Therefore, you can try to clean the device yourself, which is practiced by many car enthusiasts.

Cleaning the sensor as an alternative to replacing the flow meter

The need for cleaning can only be determined by completely disassembling the sensor. To dismantle the flow meter, you need to disconnect the six-pin plug of the detachable connection, the air intake corrugation clamp (you will need a shaped screwdriver), and two bolts securing the sensor to the air filter housing. When disassembling the sensor itself, you need to carefully remove the deflector grille so as not to damage the O-ring.

A visual inspection may show the presence of an oil film, dirt, and traces of carbon deposits on the surface of the anemometer (two wires or a film membrane). When cleaning a delicate device, the greatest danger is represented by the contacts secured with a gel-like compound. They are easy to break, so you cannot use compressed air blowing, cleaning with the tip of a knife, a sharpened match, a toothpick, or cotton swabs.

Numerous experiments have shown that most solvents are unsuitable for washing. Esters, ketones, acetone, strong solvents (“Winns”, “Abro”, “Carboklin”) dissolve the compound and can damage the membrane film. You need to be careful with the recommendations for using WD-40 and Liquid Key cleaner that contain heavy fatty acids. After washing off the deposits, these products leave an oily film on the anemometer.

The best cleaning solution is medical alcohol diluted with water, which is injected several times with a syringe. Heating the mixture (60-70 degrees) will improve cleaning results. You can dry the flow meter using a fan, naturally.

Video: checking the serviceability of the mass air flow sensor

When assembling the sensor, you must carefully install the sealing ring and check the sealing skirt. When the sensor is installed correctly, the arrow on the housing is directed towards the engine. For some flowmeter models, the axial orientation of the sensor is important. If its position is not specified in the manual, you need to mark the correct location of the anemometer during disassembly.

Prevention of air flow sensor

The only effective means of prevention for the flow meter is timely replacement of air filters. Auto mechanics do not recommend regular cleaning of the device; it can only damage the sensitive elements of the device, rendering it inoperable.

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For the most part, the stability and 100% efficiency of the engine depends on the condition of the sensors of the electronic control unit; in many cases, we are able to independently check their performance. One of these cases includes checking the mass air flow sensor DMPV, which provides the ECU with information about the amount of air consumed by the engine. Despite the seemingly overwhelming complexity of the problem, the question of how to check the mass air flow sensor can be solved independently using a conventional multimeter. The readings of the device are not yet the final verdict; checking the mass air flow sensor with a tester will only provide grounds for a subsequent decision - wash it, check it with an oscilloscope, or give it to a neighbor.

What is a mass air flow sensor?

Ten to fifteen years ago, the mass air flow sensor was widely used to operate injectors in gasoline engines; now it is the most widespread tool on domestic cars and foreign cars produced in the 2000s. The design of the mass air flow sensor is simple and reliable, with proper manufacturing quality.

In the first potentiometric versions of the mass air flow sensor, the flow rate was determined by the angle of deflection of a special lobe of the sensor, like a weather vane under the pressure of air flow. Now they are practically not used. They have been replaced by more modern options based on a platinum thermocouple or a platinum-coated silicon mass air flow sensor. Due to the high thermal conductivity of platinum, the amount of air passed through the cross-section of the air duct is easily calculated by the cooling rate of the heated air flow temperature sensor.

The air flow moving in the intake manifold, even after passing the air filter, carries microparticles of dust, soot, bitumen and tar floating in the air and exhaust gases of diesel engines, oil vapors from the crankcase ventilation system. To reduce the amount of deposits on the surface of the mass air flow (MAF), when the engine is turned off, thermal burning of dirt and organic matter occurs with a platinum element heated to white heat under the influence of electric current.

Advice! If you do not carry out preventive washing of platinum using acetone or a solvent, a situation is possible when a mixture of metal particles and massive bitumen deposits is sintered into a heat-insulating jacket, which is subsequently very difficult to remove with solvents.

Any contaminant impairs heat transfer from the platinum surface of the mass air flow sensor and distorts the readings. Checking the operation of a dirty sensor is difficult and pointless. Often, specialists at service stations replace a serviceable but dirty mass air flow sensor with a new one, without even bothering to try to wash and check it.

Possible signs of abnormal functioning of the mass air flow sensor

If the MAF readings are distorted, fuel consumption increases by almost 10-15%. The engine runs on a lean air-fuel mixture and does not develop the required power. Driving for a long time on a lean mixture will inevitably lead to burnout of the exhaust valves and melting of the catalyst mass in the exhaust manifold box.

Before checking the mass air flow sensor, pay attention to:

• overheated atmosphere in the engine compartment due to a hot exhaust manifold;
• engine traction and response have dropped by 20-30%, increased gasoline consumption;
• a sign of engine malfunction that pops up on the dashboard;
• failures during acceleration or start are replaced by normal operation; in this case, to check, it is better to replace the spark plugs with ones that are known to work.

The most accessible way to check the performance of the mass air flow sensor is to simply disconnect it from the ECU control system. If there is no control from the mass air flow sensor, the system goes into emergency operation mode. The ECU will use the average air flow recorded in the memory cells to dose gasoline consumption based on the throttle angle. You can check the operation of the system with the mass air flow sensor turned off.

In order to pre-check the mass air flow sensor, perform the following steps:

1. We disconnect the battery terminals and find the connector for the mass air flow sensor (MAF), it is easy to find on the air duct without even looking at the car’s operating manual. Typically, the sensor housing is mounted into the air pipe and secured with metal clamps.
2. We start the engine, the speed rises to more than 1200 rpm. When starting and picking up speed, we can check the change in acceleration dynamics and engine response.

Advice! There is absolutely no point in overusing such checks; the sensor readings actively affect the stable operation of the ECU and the correction of engine speed. Despite the external operability of the engine, long-term use of the ECU emergency mode is not recommended.

How to remove and check the performance of the mass air flow sensor

There are many factors that can influence changes in driving dynamics, and it is also difficult to assess the performance of the mass air flow sensor based on subjective sensations. It would be more reliable to check the MAF sensor with a multimeter or tester, but such measurements are possible for original BOS products with catalog items 0 280 218 004, 0 280 218 037, 0 280 218 116.

To gain access to the contacts, remove the silicone rubber from the connector block, do not touch the mass air flow sensor itself, and carefully insert the positive probe of the multimeter into the rightmost wire (yellow) and, accordingly, the negative one into the third wire from the left (green). You will have to measure potential values ​​from 0.9-1.5V, so it is better to use the most sensitive DC voltage measurement range in the device.

Advice! Connect the negative probe directly to the connector, and not with a standard ground contact. Otherwise, an error of 5-7% will be introduced into the multimeter readings.

Preliminary conclusions

The sensor must be properly tested. The maximum permissible potential value for a working mass air flow sensor is 1.4 V. The value for normal “health” of the sensor is 1.01 V. These are the limits of serviceability; at 1.5V and above the device is considered to be out of order.

Attention! All measurements are carried out with a warmed-up, switched off engine with the ignition switch on or idling.

Let's try to restore the mass air flow sensor

If the age of your car still allows you to hope for a miracle, and you are sure that the mass air flow sensor is of original origin, it makes sense to carry out a small procedure to remove contaminants from the platinum surface.

To resuscitate an expensive device, we use a special liquid in an aerosol package, recommended for cleaning and servicing internal combustion engine carburetors. Before washing the sensor, remove it from the air duct pipe, first unscrewing the bolts on the mounting clamps. To remove the platinum substrate, you need to unscrew two screws using a torx screwdriver and carefully pull out the mass air flow sensor board.

A thin wire or metal-ceramic element must be treated with liquid several times without touching it with hands or tools to avoid scratches. The fluid flow rate is chosen at your own discretion. After the procedure, it is necessary to check the quality of washing. An alternative to an aerosol can be a mixture of alcohol and acetone, with a strong jet of clean compressed air.

If there are black spots or signs of deep erosion of the working surface, the mass air flow sensor should be subjected to a soaking procedure by applying an acetone-soaked swab to the wire for several hours.

At the end of the procedure, we assemble the sensor; you need to re-check the mass air flow sensor with a multimeter. In most cases, the device’s functionality is restored, although at the minimum possible level. You can even calculate and check the air flow using the multimeter readings,

For your information

You can check and make the most reliable diagnosis of the performance of the mass air flow sensor (MAF) using an oscillogram of its operation using specialized diagnostics, but it is not cheap. Before purchasing a new mass fuel flow sensor, carefully examine the device itself and its packaging box. Chinese craftsmen have launched the production of counterfeit sensors on a decent scale, so you need to pay attention to the main signs of a fake:

• pungent odor and poor quality of the plastic from which the case is made;
• The seal gasket is not made of elastic silicone, but of hard and brittle rubber;
• The product is packaged in a regular cardboard box marked BOSH in black, not red, without the use of oiled paper or a special bag.

Alternatively, in case of emergency, you can buy a used working ear sensor at a service station, especially since you can check it.

Video on how to check the performance of the mass air flow sensor:

For optimal operation of an injection internal combustion engine (hereinafter referred to as ICE), it is necessary to take into account how much air mixture enters the combustion chambers of the cylinders. Based on these data, the electronic control unit (hereinafter referred to as the ECU) determines the fuel supply conditions. In addition to information from the mass air flow sensor, its pressure and temperature are taken into account. Since mass air flow sensors are the most significant, we will consider their types, design features, diagnostic and replacement capabilities.

Purpose and explanation of the abbreviation

Flow meters, also known as volume meters or mass air flow meters (not to be confused with mass air flow meters and mass air flow sensors), are installed in diesel or gasoline-powered vehicles. The location of this sensor is not difficult to find, since it controls the air supply, you should look for it in the corresponding system, namely, after the air filter, on the way to the throttle valve (DZ).

The device is connected to the engine control unit. In cases where the mass air flow sensor is in a faulty condition or is missing, a rough calculation can be made based on the position of the air flow sensor. But with this measurement method it is impossible to ensure high accuracy, which will immediately lead to excessive fuel consumption. This once again indicates the key role of the flow meter in calculating the fuel mass supplied through the injectors.

In addition to information from the mass air flow sensor, the control unit also processes data coming from the following devices: camshaft sensor (camshaft sensor), DD (knock meter), remote sensor, cooling system temperature sensor, acidity meter (lambda probe), etc.

Types of mass air flow sensors, their design features and operating principle

Three types of VU meters are most widespread:

• Wire or thread.
• Film.
• Volumetric.

In the first two, the operating principle is based on obtaining information about the mass of the air flow by measuring its temperature. The latter may involve two accounting options:

Vortex sensor design (widely used by Mitsubishi Motors)

Designations:

• A – pressure measurement sensor to record the passage of the vortex. That is, the frequency of pressure and vortex formation will be the same, which makes it possible to measure the flow of the air mixture. At the output, using an ADC, the analog signal is converted to digital and transmitted to the ECU.
• B - special tubes that form an air flow similar in properties to laminar.
• C – bypass air ducts.
• D – column with sharp edges on which Karman vortices are formed.
• E – holes used to measure pressure.
• F – direction of air flow.

Wire sensors

Until recently, thread mass air flow sensor was the most common type of sensor installed on domestic cars of the GAZ and VAZ model range. An example of a wire flow meter design is shown below.

Designations:

• A – Electronic board.
• B – Connector for connecting the mass air flow sensor to the computer.
• C – CO adjustment.
• D – Flow meter housing.
• E – Ring.
• F – Platinum wire.
• G – Resistor for temperature compensation.
• N – Ring holder.
• I – Electronic board casing.

Operating principle and example of a functional diagram of a filament VU meter.

Having understood the design of the device, let's move on to the principle of its operation, it is based on the hot-wire method, in which a thermistor (RT), heated by the current passing through it, is placed in the air flow. Under its influence, the heat transfer changes, and, accordingly, the resistance RT, which makes it possible to calculate the volumetric flow rate of the air mixture? using King's equation:

I 2 *R=(K 1 +K 2 * ⎷ Q )*(T 1 -T 2) ,

where I is the current passing through RT and heating it to temperature T1. In this case, T 2 is the ambient temperature, and K 1 and K 2 are constant coefficients.

Based on the above formula, you can derive the volumetric air flow rate:

Q = (1/K 2)*(I 2 *R T /(T 1 – T 2) – K 1)

An example of a functional diagram with bridge connection of thermoelements is shown below.

Designations:

• Q - measured air flow.
• U – signal amplifier.
• R T - wire thermal resistance, as a rule, is made of platinum or tungsten filament, the thickness of which is in the range of 5.0-20.0 microns.
• R R – temperature compensator.
• R 1 -R 3 – ordinary resistances.

When the flow velocity is close to zero, the RT is heated to a certain temperature by the current passing through it, which allows the bridge to be kept in equilibrium. As soon as the flow of the air mixture increases, the thermistor begins to cool, which leads to a change in its internal resistance, and, as a result, an imbalance in the bridge circuit. As a result of this process, a current is generated at the output of the amplifier unit, which partially passes through the temperature compensator, which leads to the release of heat and makes it possible to compensate for its loss from the flow of the air mixture and restores the balance of the bridge.

The described process allows you to calculate the flow rate of the air mixture based on the amount of current passing through the bridge. In order for the signal to be perceived by the ECU, it is converted into a digital or analog format. The first allows you to determine the flow rate by the frequency of the output voltage, the second - by its level.

This implementation has a significant drawback - a high temperature error, so many manufacturers add a thermistor similar to the main one to the design, but do not expose it to air flow.

During operation, dust or dirt deposits may accumulate on the wire thermistor; to prevent this, this element is subjected to short-term high-temperature heating. It is performed after the internal combustion engine is turned off.

Film air meters

A film MAF works on the same principle as a filament one. The main differences lie in the design. In particular, silicon crystal is used instead of platinum filament resistance wire. It is coated with several layers of platinum plating, each of which plays a specific functional role, namely:

• Temperature sensor.
• Thermal resistances (usually there are two of them).
• Heating (compensation) resistor.

This crystal is installed in a protective casing and placed in a special channel through which the air mixture passes. The geometry of the channel is designed in such a way that temperature measurements are taken not only from the input flow, but also from the reflected one. Thanks to the created conditions, a high speed of movement of the air mixture is achieved, which does not contribute to the deposition of dust or dirt on the protective housing of the crystal.

Designations:

• A – Flow meter body into which the measuring device (E) is inserted.
• B – Contacts of the connector that connects to the ECU.
• C – Sensitive element (silicon crystal with several layers of coating, placed in a protective casing).
• D – Electronic controller, with the help of which preliminary processing of signals is carried out.
• E – Body of the measuring device.
• F - Channel configured to take thermal readings from the reflected and input flow.
• G – Measured flow of air mixture.

As mentioned above, the operating principles of filament and film sensors are similar. That is, the sensitive element is initially heated to temperature. The flow of the air mixture cools the thermoelement, which makes it possible to calculate the mass of the air mixture passing through the sensor.

As in filament devices, the output signal can be analog or converted to digital format using an ADC.

It should be noted that the error of filament VU meters is about 1%; for film analogues this parameter is about 4%. However, most manufacturers have switched to film sensors. This is explained both by the lower cost of the latter and by the expanded functionality of the ECUs that process information from these devices. These factors overshadowed the accuracy of the instruments and their speed.

It should be noted that thanks to the development of flash microcontroller manufacturing technology, as well as the introduction of new solutions, it was possible to significantly reduce the error and increase the performance of film structures.

Interchangeability

This issue is quite relevant, especially taking into account the cost of original products from the imported automobile industry. But it’s not so simple here; let’s give an example. In the first production models of the Gorky Automobile Plant, the injection Volgas were equipped with a BOSCH air flow sensor. Somewhat later, imported sensors and controllers replaced domestic products.

A – imported filament air flow sensor manufactured by Bosh (pbt-gf30) and its domestic analogues B – JSCB “Impuls” and C – APZ

Structurally, these products were practically no different with the exception of several design features, namely:

• The diameter of the wire used in a wirewound thermistor. Bosch products have a diameter of 0.07 mm, and domestic products have a diameter of 0.10 mm.
• The method of fastening the wire differs in the type of welding. For imported sensors this is resistance welding, for domestic products it is laser welding.
• Shape of a thread thermistor. Bosh has a U-shaped geometry, APZ produces devices with a V-shaped thread, and products from JSC Impulse are distinguished by the square shape of the thread suspension.

All the sensors given as an example were interchangeable until the Gorky Automobile Plant switched to film analogues. The reasons for the transition were described above.

Film air flow sensor Siemens for GAZ 31105

It makes no sense to give a domestic analogue to the sensor shown in the figure, since outwardly it is practically no different.

It should be noted that when switching from filament devices to film devices, most likely, it will be necessary to change the entire system, namely: the sensor itself, the connecting wire from it to the ECU, and, in fact, the controller itself. In some cases, the control can be adapted (reflashed) to work with another sensor. This problem is due to the fact that most filament flowmeters send analog signals, while film flowmeters send digital signals.

It should be noted that the first production VAZ cars with an injection engine were equipped with a filament air flow sensor (made by GM) with a digital output; examples include models 2107, 2109, 2110, etc. Now they are equipped with air flow sensor BOSCH 0 280 218 004 .

To select analogues, you can use information from official sources or thematic forums. As an example, below is a table of the interchangeability of mass air flow sensors for VAZ cars.

The presented table clearly shows that, for example, the MAF sensor 0-280-218-116 is compatible with VAZ 21124 and 21214 engines, but is not suitable for 2114, 2112 (including those with 16 valves). Accordingly, you can find information on other VAZ models (for example, Lada Granta, Kalina, Priora, 21099, 2115, Chevrolet Niva, etc.).

As a rule, there will be no problems with other brands of cars of domestic or joint production (UAZ Patriot ZMZ 409, Daewoo Lanos or Nexia), choosing a replacement mass air flow sensor for them will not be a problem, the same applies to products of the Chinese automobile industry (KIA Ceed, Spectra, Sportage etc.). But in this case, there is a high probability that the MAF pinout may not match; a soldering iron will help correct the situation.

The situation is much more complicated with European, American and Japanese cars. Therefore, if you have a Toyota, Volkswagen Passat, Subaru, Mercedes, Ford Focus, Nissan Premiere P12, Renault Megane or another European, American or Japanese car, before replacing the mass air flow sensor, you need to carefully weigh all the solution options.

If you are interested, you can search online for an epic about an attempt to replace the “native” air meter with an analogue on a Nissan Almera H16. One attempt resulted in excessive fuel consumption even at idle.

In some cases, searching for an analogue one will be justified, especially if you take into account the cost of the “native” VU meter (for example, the BMW E160 or Nissan X-Trail T30).

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)

Example of the "Cheeck Engine" message displayed (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, diagnostics must be performed. 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.

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).

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.

Briefly about the renovation

As a rule, MAF sensors that have become unusable cannot be repaired, except in cases where they require washing and cleaning.

In some cases, it is possible to repair the volumetric air flow sensor board, but this process will not prolong the life of the device for long. As for the boards in film sensors, without special equipment (for example, a programmer for a microcontroller), as well as skills and experience, it is pointless to try to restore them.