What happens if the air flow meter does not work. What are dmrv

Designed to provide information about the amount of air entering the engine cylinders internal combustion on the ECU. These devices are conditionally divided into several types - mechanical, film (hot-wire and diaphragm), pressure sensors. The first type is considered obsolete and rarely used, while the rest are more common. There are a number of typical signs and reasons why a flow meter completely or partially fails. Next, we will look at them, and also talk about how to check, repair or replace the flow meter.

What is a flow meter

As mentioned above, flow meters are designed to indicate the volume and control of the air consumed by the engine. Before proceeding to the description of the principle of their work, it is necessary to touch on the issue of types. After all, his work will depend on this.

Types of flowmeters

Appearance of the flowmeter

The very first models were mechanical and installed on the following fuel injection systems:

• distributed injection Jetronic;
• combined system of electronic injection and electronic ignition Motronic;
• K-Jetronic;
• KE-Jetronic;
• L-Jetronic.

The housing of the mechanical flowmeter contains a damping chamber, a measuring damper, a return spring, a damping damper, a potentiometer, and a bypass (bypass channel) with an adjustable regulator.

In addition to mechanical flow meters, there are also the following types of more advanced devices:

• heated filament flow meter;
• flow meter with hot film anemometer;
• flow meter with thick-walled diaphragm;
• manifold air pressure sensor.

The principle of operation of the flowmeter

Scheme of a mechanical flowmeter. 1 - voltage supply from the electronic control unit; 2 – incoming air temperature sensor; 3 - air supply from the air filter; 4 - spiral spring; 5 - damping chamber; 6 – damping chamber damper; 7 - air supply to the throttle valve; 8 - air pressure damper; 9 - bypass channel; 10 - potentiometer

Let's start with mechanical flowmeter. Its principle of operation is based on how far the measuring flap moves depending on the volume of air it passes. On the same axis as the measuring flap there is also a damping flap and a potentiometer (adjustable voltage divider). The latter is made in the form electronic circuit with soldered resistor tracks. In the process of turning the damper, the slider moves along them, and thus the resistance changes. Accordingly, the voltage that the potentiometer transmits is measured in accordance with positive feedback, and transmitted to the electronic control unit. To correct the operation of the potentiometer, an intake air temperature sensor is also included in its circuit.

However, mechanical flow meters are now considered obsolete as they have been replaced by their electronic counterparts. They do not have moving mechanical parts, therefore they are more reliable, give more accurate results, and their operation does not depend on the temperature of the intake air.

Another name for such flowmeters is sensor mass flow air. In turn, they are divided into two types depending on the sensing element used:

• wire (Hot Wire MAF Sensor);
• film (Hot Film Air Flow Sensor, HFM).

Air mass meter with wire heating element (thread). 1 – temperature sensor; 2 – sensor ring with wire heating element; 3 - precision rheostat; Qm - mass air flow per unit time

The operation of devices of the first type is based on use of heated platinum filament. The electrical circuit constantly keeps the thread in a heated state (platinum is chosen due to the fact that the metal has a low resistivity, does not oxidize and is not affected by aggressive chemical factors). The design provides that the passing air cools its surface. The electrical circuit has a negative feedback, according to which, as the thread cools, more electricity in order to keep the temperature constant.

Also in the circuit there is a converter, the task of which is to translate the value of the changing current into a potential difference, that is, voltage. There is a non-linear exponential relationship between the obtained voltage value and the passed air volume. The exact formula is programmed into the ECU, and in accordance with it, he decides how much air is needed at one time or another.

The design of the wire flow meter implies a so-called self-cleaning mode. In this case, the platinum thread is heated to a temperature of +1000°C. As a result of heating, various chemical elements, including dust. However, due to such heating, the thickness of the thread gradually decreases. This leads, firstly, to errors in the readings of the sensor, and secondly, to the gradual wear of the thread itself.

Scheme mass flow meter air with a hot film anemometer. 1 - electrical connector pins, 2 - measuring pipe or air filter housing, 3 - computing circuit (hybrid circuit), 4 - air inlet, 5 - sensor sensing element, 6 - air outlet, 7 - bypass channel, 8 - sensor housing.

Now let's look at work film mass air flow sensor. They are of two types - with a hot-film anemometer and based on a thick-walled diaphragm. Let's start the description from the first.

It is the result of the evolution of a wire flow meter, however, instead of a wire, in this case, a silicon crystal is used as a sensitive element, on the surface of which several layers of platinum are soldered, which are used as resistors. In particular:

• heating resistor;
• two thermal resistors;
• intake air temperature sensor resistor.

By analogy with a wire-wound flow meter, the sensing element is located in the channel through which the air passes. It is in a constantly heated state due to the use of a heating resistor. When it enters the channel, the air changes its temperature, which is fixed with the help of thermistors installed at both ends of the channel. The difference in their readings at the two ends of the diaphragm is the potential difference, that is, a constant voltage (ranging from 0 to 5 V). Most often, this analog signal is digitized in the form of electrical impulses that are transmitted directly to the car's ECU.

The principle of measuring the mass air flow with a hot-film anemometer. 1 - temperature characteristic in the absence of air flow 2 - temperature characteristic in the presence of air flow; 3 - sensitive element of the sensor; 4 – heating zone; 5 – sensor diaphragm; 6 – sensor with measuring branch pipe; 7 - air flow; М1, М2 – measurement points, Т1, Т2 – temperature values ​​at measurement points M1 and М2; ΔT - temperature difference

As for the second type of film flowmeter, they are based on the use of a thick-walled diaphragm located on a ceramic base. Its active sensor detects changes in the vacuum in the intake manifold based on the deformation of the film diaphragm. With significant deformation, a corresponding dome is obtained with a diameter of 3 ... 5 mm and a height of about 100 microns. Inside are piezoelectric elements that convert the mechanical action into electrical signals, which are then transmitted to the computer.

AT modern machines that use electronic ignition are used air pressure sensors, which are considered more technologically advanced than classical flow meters operating according to the schemes described above. The sensor is located in the manifold and determines the pressure and load of the engine, as well as the amount of recirculated gases. In particular, it is connected to the intake manifold with a vacuum hose. During operation, a vacuum occurs in the collector, which acts on the sensor membrane. Directly on the membrane are strain gauges, whose electrical resistance varies depending on the position of the membrane.

The sensor operation algorithm consists in comparing the atmospheric pressure and the pressure on the membrane. The larger it is, the greater the change in resistance, and hence the voltage supplied to the computer. The sensor power supply is 5 V DC, and the control signal is a pulse with a constant voltage of 1 to 4.5 V (in the first case, this is an idle engine, in the second, the engine is running at maximum load). The ECU directly calculates the mass amount of air, also based on the density of the air, its temperature, as well as the number of revolutions of the crankshaft.

Due to the fact that the mass air flow sensor is a rather vulnerable device and often fails, since about the beginning of the 2000s, automakers began to abandon its use in favor of using engines with an air pressure sensor.

Film air flow meter. 1 - measuring circuit; 2 - diaphragm; 3 – reference pressure chamber; 4 - measuring elements; 5 - ceramic substrate

Using the received data, the electronic control unit regulates following parameters. For petrol engines:

• moment of fuel injection;
• its quantity;
• moment of ignition initiation;
• operation algorithm of the gasoline vapor recovery system.

For diesels:

• moment of fuel injection;
• algorithm of the exhaust gas recirculation system.

As you can see, the sensor device is simple, but it performs a number of key functions, without which the operation of internal combustion engines would be impossible. Now let's move on to considering the signs and causes of malfunctions of this node.

Signs and causes of malfunctions

In the event of a partial failure of the flow meter, the driver will notice one or more of the following situations. In particular:

• the engine does not start;
• unstable operation (floating speed) of the engine in idle mode, up to its shutdown;
• the dynamic characteristics of the car are reduced (during acceleration, the engine “fails” when you press the accelerator pedal);
• significant excessive fuel consumption;
• on the dashboard control lights up.

These symptoms may be the result of other malfunctions. individual elements engine, but among other things it is necessary to check the operation of the air mass meter. Now consider the reasons why the described malfunctions occur:

• Natural aging and sensor failure. This is especially true for relatively old machines that have an original flow meter installed.
• Motor overload. Due to overheating of the sensor and its individual elements, it may provide incorrect data for the computer. This arises due to the fact that with significant heating of the metal, its electrical resistance changes, and, accordingly, the calculated data on the amount of air passing through the device.
• Mechanical damage to the flowmeter. It may be the result various activities. For example, damage when replacing the air filter or other components close to it, broken contacts during installation, and so on.
• Moisture ingress into the case. The reason is quite rare, but it can occur if, for some reason, it gets into the engine compartment a large number of water. This may cause short circuit in the sensor circuit.

As a rule, the flowmeter cannot be repaired (with the exception of mechanical samples), and if it fails, it must be replaced. Fortunately, the device is inexpensive, and the process of dismantling and installation does not take much effort and time. However, before replacing, it is necessary to diagnose the sensor and try to clean the sensitive element with a carburetor cleaner.

How to check the air mass meter

The air mass meter test process is simple and can be done in several ways. Let's consider them in more detail.

Disabling the sensor

The simplest method is to turn off the flowmeter. To do this, with the engine turned off, disconnect the supply wire suitable for the sensor (usually red-black). Then start the engine and drive the car. If on dashboard the Check Engine control lamp lit up, the idle speed exceeded 1500 rpm, and the dynamics of the car improved, which means that with a high degree of probability it can be argued that yours is faulty. However, we recommend that you perform additional diagnostics.

Checking with a scanner

Another diagnostic method is using a special scanner for detecting errors in car systems. Currently, there is a wide variety of such devices. More professional models used in workshops or service centers. However, for the average car owner there is a simpler solution.

It consists in installing a special software on a smartphone or tablet with the Android operating system. Using a cable and an adapter, the gadget is connected to the car's ECU, and the mentioned program allows you to get information about the error code. To decipher them, you need to use the reference literature.

Popular adapters:

• K-Line 409.1;
• ELM327;
• OP-COM.

As for software, most often car owners use the following software:

• Torque Pro;
• OBD Auto Doctor;
• ScanMaster Lite;
• bmwhat.

Most common error codes:

• P0100 - mass or volume air flow sensor circuit;
• P0102 - low signal level at the input of the mass or volumetric air flow sensor circuit;
• P0103- high level signal at the input of the mass or volumetric air flow sensor circuit.

Using the listed hardware and software tools, you can not only search for an air mass meter error, but also make additional settings for installed sensor or other vehicle components.

Checking the flow meter with a multimeter

Checking the MAF with a multimeter

Also among motorists, a method of checking the flow meter with a multimeter is popular. Since the BOSCH DMRV is the most popular in our country, the verification algorithm will be described specifically for it:

1. Turn on the multimeter in the DC voltage measurement mode (in the English abbreviation - DC). Set the upper limit so that the device can detect voltages up to 2 V.
2. Start the car engine and open the hood.
3. Find the air flow meter directly. It is usually located on or behind the air filter housing.
4. The red probe of the multimeter must be connected to yellow wire on the sensor, and black to green.
5. If the sensor is working, then the voltage value on the multimeter screen should not exceed 1.05 V. If the voltage is much higher, then the sensor is completely or partially out of order.

Here is a table for you, which indicates the value of the received voltage and the state of the sensor.

Visual inspection and cleaning of the air mass meter

If you do not have a scanner or the appropriate software to diagnose the condition of the mass air flow sensor, you should perform a visual inspection of it in order to identify a malfunction of the air flow meter. The fact is that situations are not uncommon when dirt, oil or other process fluids get into its body. This results in errors in the data output by the device.

For visual inspection The first step is to dismantle the flow meter. Each model of the machine may have its own nuances, but in general, the algorithm will be approximately as follows:

1. Turn off vehicle ignition.
2. Using a wrench (usually 10 wrench), disconnect the air hose through which air enters it.
3. Disconnect the wires listed in the previous paragraph from the sensor.
4. Carefully remove the sensor without losing the O-ring.

Next, you need to conduct a visual inspection. In particular, you need to make sure that all visible contacts are in normal condition, not broken or oxidized. Also check for dust, debris, and process fluids both inside the housing and directly on the sensing element. Their presence can cause errors in the broadcast readings.

Accordingly, if these contaminants are detected, it is necessary to clean the housing and the sensing element. For this it is best to use air compressor and rags ( with the exception of the film flow meter, clean or blow through compressed air it is forbidden).

Perform the cleaning procedure carefully so as not to damage its internal elements, especially the threads.

Results

Finally, we will give a few more tips on how to extend the life of the air mass meter. First, change regularly air filter. Otherwise, the sensor will overheat and give incorrect data. Secondly, do not allow the general overheating of the motor and make sure that the cooling system works in normal mode. Thirdly, in case of cleaning the air mass meter, perform this procedure carefully. Unfortunately, most modern DMRVs cannot be repaired, therefore, if they fail completely or partially, an appropriate replacement must be made.

In modern cars with injection engines, electronics are responsible for preparing the working mixture. The quality of the working mixture depends on the ratio in which the fuel is mixed with air. Depending on the amount of air passing through the throttle valve, the electronic engine control unit determines how much fuel must be supplied to the cylinders. To determine the amount of air entering the engine, a mass air flow sensor or DMRV is used; in some sources the name "volumeter" is found.

"Where is the DMRV?" - inexperienced car owners are interested. The specified sensor is installed in the intake air tract immediately behind the air filter; it is connected to the control unit using a six-pin block.

In theory, the process of measuring the amount of air passing through the throttle valve is not particularly difficult. If you press the gas pedal, the damper opens, and it will be easier for air to get inside, when released, on the contrary, much less air is sucked in. However, the engine constantly works in different modes, the driver either presses or releases the gas pedal, and, constantly in different ways, besides, turbulence occurs in the intake tract, so in reality the task will be many times more difficult.

What are DMRV

Depending on the structure, several types of mass air flow sensors are distinguished. The most common are:

• mechanical (vane);
• ultrasonic;
• hot-wire anemometric (the latter are used, in particular, on VAZ vehicles).

The device and principle of operation of the DMRV

There are no moving parts in the mass air flow sensor. This increases its service life. The principle of its work is the following. The sensing element of the first sensors developed by the Bosch mould, is a platinum wire or a nickel mesh. An electric current is supplied to the element, which heats it. If the system is wire, then the thermoelement will be heated to a temperature 100 degrees higher than the temperature of the incoming air, the temperature of the nickel mesh is 75 degrees higher than the temperature of the incoming air.

The incoming air stream cools the sensing element, therefore more current is needed to maintain its temperature. By how much the current has increased, the engine control unit determines how much air enters the engine. Some DMRVs produced frequency output signals, i.e. their variable was the frequency of the output pulses. Such mass air flow sensors were used in the engines of VAZ vehicles equipped with the January-4.1 controller.

Modern MAFs, installed, including on VAZ vehicles, have a more complex device. Instead of a wire or mesh, they have a thin film as a sensitive element, on which temperature sensors are placed and a heating element. The principle of operation of the DMRV of VAZ cars is slightly different. In the center of the film there is a heating zone, the degree of its heating is controlled by thermal sensors. On both sides of the film there are two additional thermal sensors, i.e. one is directly in the path of the airflow, and the second is hidden behind the film. When the car is stationary, the temperature of both sensors is the same, while driving, the first sensor is cooled by the incoming air flow, and the second has a practically constant temperature. The temperature difference of the temperature sensors is directly proportional to the mass of the intake air.

Which DMRV is better

Each sensor has its own advantages and disadvantages, so it is impossible to unambiguously answer this question. The wire-wound mass air flow sensor has high reliability. This is its main advantage, which can overcome all the shortcomings, including the lower measurement accuracy compared to the film DMRV, and the inability to register the reverse air flow.

The film sensor, which is installed on modern VAZ engines, due to the presence of two thermal sensors, is able to register the return air flow (if the temperature of the second sensor is lower than the first), in addition, the accuracy of its measurements is very high. Main disadvantage sensor - it is afraid of dirt and moisture, so if the car owner wants the sensor to work smoothly, he needs to carefully monitor the condition of the air filter.

Is it possible to drive without a DMRV

It often happens that the mass air flow sensor fails. Since not every car can easily go and buy it, many car owners are wondering: “Is it possible to drive without a DMRV?”

If you turn off the DMRV, the control unit goes into emergency mode. The fuel-air mixture is prepared depending on the position of the throttle valve, as a result, fuel consumption increases, and the crankshaft speed does not fall below 1500 rpm.

By the way, in this way you can check the health of the sensor. If the car becomes faster when it is turned off, then the DMRV is faulty.

Interchangeability of DMRV for VAZ cars

Some owners of VAZ cars are interested in what will happen if they install another DMRV instead of the standard one, and how safe such an improvement is.

Mass air flow sensors are designed for a specific engine, and have different output voltages at the same air flow. Therefore, if you install the wrong sensor, which is needed, the ECU will not be able to correctly interpret its readings. The result will be, at a minimum, an increase in fuel consumption, as a maximum - the engine simply will not work.

Nevertheless, if absolutely necessary, if a standard sensor cannot be found anywhere, you can “reflash” it to the parameters of the DMRV, designed for another VAZ engine. However, this should be done with extreme caution, since it is likely to completely disable the computer.

The precise operation of an injection or diesel engine depends on the accuracy of the sensors serving it. Should one of the sensors fail, the entire control system is rebuilt beyond recognition in order to make the engine work in optimal mode. And one of the most important sensors is the one that determines the amount of air consumed by the engine at a given moment.

During operation, the engine consumes not only expensive fuel, but also free air. Moreover, according to the laws of the physico-chemical process of fuel ignition in the combustion chamber, the engine needs about 12-14 liters of air to burn a liter of fuel. Only then the combustion efficiency will be maximum, only then there will be no excessive fuel consumption and then the amount of toxic emissions will be minimal. Fuel is easier. How much the nozzle filed into the cylinder, so much fuel burned out. How much gasoline was bought, so much of his pump was pumped into the fuel frame. So far, the air is released into one hand unlimitedly, if we talk about the process of fuel combustion, then oxygen must be clearly controlled. That's why they install the DMRV, the mass air flow sensor.

The MAF measures the exact amount of air entering the cylinder and transmits this information to the electronic engine control unit. The ECU, in turn, based on this data, draws conclusions about how much fuel needs to be supplied. The DMRV, of course, is not the last resort that affects the fuel supply, but its testimony in this case is very important.

The principle of operation of the DMRV

To determine the engine load and the amount of mixture that is needed to operate the engine in this mode, the ECU makes calculations every second to make the correct mixture ratio. By pressing the accelerator pedal, we open the air damper, which allows a certain amount of air to pass through, and the exact amount is determined by the sensor.

The sensor itself is arranged in front of the throttle valve, and it consists of a platinum-plated conductor with a thickness of about 70 microns. In general, there are two types of sensors:

1. Mechanical.
2. Thermal.

The mechanical sensor simply determines the air volume based on the throttle position. Now such sensors are not used in internal combustion engines. The thermal method of measuring the air flow takes into account the heating of the platinum element. Sensors are usually installed between the filter and the throttle in the intake tract.

DMRV malfunctions in diesel engines and injection engines

Since the mixture formation adjustment is based on the readings of the MAF, its failure can significantly affect the operation of the engine as a whole. Sometimes the symptoms of a malfunctioning DMRV can be expressed in a complete engine failure, it would seem, for no apparent reason. There are, however, less disturbing, but more telling symptoms that the sensor is not working correctly or has failed at all.

Since the sensors thermal type are installed in diesel engines, then the symptoms may be identical. Diesel-only symptoms include characteristic black smoke from exhaust pipe, but it cannot guarantee an accurate diagnosis. The symptoms are familiar to those who have encountered completely different problems in the operation of the motor, so they alone cannot be used to judge the condition of the sensor. If there are suspicions about the correctness of its readings, the sensor must be checked.

How to test the mass air flow sensor

Insofar as mechanical sensors Since we no longer use, but use only thermoelectric ones, then we will measure the electrical parameters of the sensor to check it. Although the most children's way sensor checks - on idling just remove the block from the MAF connector. As soon as the block is turned off, the ECU loses the sensor from the field of view and gives a signal about emergency operation, while in the meantime it is guided by the readings of the damper angle sensor. At this point, you can find out if the DMRV is working or not. After disconnecting the pads, the engine may start to work intermittently and idle will float. On a warm engine, you can drive several kilometers with the sensor turned off. If traction appears and power visually increases, the sensor is unusable.

You can also check by measuring the signal on the far right wire. If the sensor is working, the voltage on the leg will be in the range of 1-1.5 V. If the reading is higher, the sensor is faulty and must be replaced or flushed. So simple ways it is possible to preliminarily determine the malfunction of the DMRV without diagnostic equipment. Do not dirty the sensor, and good luck to everyone!

Listening from auto mechanics to the results of machine diagnostics, repair forecasts, very often the DMRV (mass air flow sensor) is mentioned as possible reason malfunctions. It is practically not subject to repair, and replacement costs a tidy sum. Sometimes, having made 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 a correct understanding of the operation of the sensor will save time and money for the motorist.

DMRV - what is it, mass air flow sensor function

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 assume that the sensor regulates the air flow. Based on the indicators of the meter, 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 passenger cars, the meter is supplemented with correlating sensors for temperature and atmospheric air pressure. Multi-sensor readings help control ignition timing, improving engine efficiency.

Mechanism of operation of the flow meter, DMRV design

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 (vane flowmeters with Pitot tubes), the potentiometer measures the amount of vane in the vane.

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

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

Structurally, the air flow meter consists of a plastic cylindrical pipe, inside which a hot-wire anemometric meter is mounted. The air intake is made through a lattice deflector (metal or plastic), equipped with rubber sealing rings. Connector electrical circuit, with power supply wires, the signal to the ECU is located on outside device. The device is placed between the air filter and the engine.

Causes of failure, signs of failure

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

Signs of a malfunction of the meter are:

1. Engine RPM fluctuations at idle.
2. The appearance of the "check" signal on the on-board computer display.
3. Dips in engine power when using the accelerator.
4. Stops the engine in motion.
5. Increase in fuel consumption.

It is impossible to consider such symptoms as an unambiguous indication of a breakdown of the flow meter; similar symptoms occur when there are malfunctions of the throttle valve, EGR valve, fuel pump, and ignition module. The final answer is possible only with the diagnosis of the meter.

The ECU responds to failures in the readings of the flow meter 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 indicators.

Self test sensor

To independently check the electrical signals of the flowmeter, which is not particularly difficult, you will need a multimeter. The first step is to diagnose the performance of the plug-in connection (chips). To do this, on the removed chip, the red-black connector is checked with the positive probe of the tester. By attaching the second probe to the stripped 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 chips.

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

1. Light yellow. Signal input.
2. Grey-white. Sensor power cable.
3. Green. Flowmeter grounding.
4. Pink black or white. signal to the ECU.

Having connected the connector to a regular place, we check the readings on an idle engine. The mass probe remains in the same place during further tests. By inserting the positive probe into the fourth wire, we get the readings of the transmitting signal to the computer. The standard signal voltage of a serviceable flow meter ranges from 1.0 to 1.02 volts. Readings above 1.05 volts indicate the need to replace the sensor.

At idle (the engine needs to be warmed up), the standard readings vary from 1.2 to 1.8 volts. To check the efficiency of the DMRV, we check the readings with several throttle openings. An increase in engine speed should cause an increase in signal strength.

Device maintainability

Vane sensors are considered conditionally repairable, although in practice auto mechanics refuse to repair them. The real repair of the flow meter is reduced to the replacement of the device assembly. The operations of dismantling, installing the device are simple, the cost of replacement is increased by the need for several types of diagnostics, checking other components that cause identical engine behavior. The selection of a sensor for replacement must be trusted by an experienced auto mechanic, knowing the features your car model.

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

Cleaning the sensor as an alternative to replacing the flowmeter

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

Visual inspection may show the presence of an oil film, dirt, carbon deposits on the surface of the anemometer (two wires or a film membrane). When cleaning a delicate device, the contacts fixed with a gel-like compound are the most dangerous. They are easy to tear off, so blowing with compressed air, cleaning with the tip of a knife, a pointed match, a toothpick, cotton swabs should not be used.

Numerous experiments have shown unsuitability for washing most solvents. Ethers, ketones, acetone strong solvents ("Winns", "Abro", "Carboclin") dissolve the compound and can damage the membrane film. Caution should be taken when using WD-40, Liquid Key cleaner containing heavy fatty acids. After washing off the soot, these products leave an oily film on the anemometer.

The best flushing agent is diluted with water. medical alcohol, which is injected several times with a syringe. Heating the mixture (60-70 degrees) will improve cleaning results. You can dry the flowmeter with a fan, in a natural way.

Video: check the health of the DMRV

When assembling the sensor, you need to carefully install the sealing ring, check the sealing skirt. At correct installation The arrow on the housing points towards the engine. For some flowmeter models, the axial orientation of the sensor is important. If its position is not specified in the manual, it is necessary to mark during disassembly correct location anemometer.

Prevention of DMRV

the only effective means Prevention for the flow meter is the 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 unusable.

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The efficient operation of the engine depends on the quality of the incoming air-fuel mixture. In modern cars, the control unit calculates the amount of fuel needed depending on the amount of air that has entered the system. It receives this information from the air mass meter. If it is faulty, it will transmit incorrect readings that will affect the operation of the engine. The article deals with issues related to the DMRV: signs of malfunction, verification, repair and replacement.

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Symptoms

The MAF is located in the air duct near the air filter. It is designed to determine the amount of incoming air. Depending on its readings, the control unit will show how much fuel is needed to form a high-quality fuel mixture. A ratio of 1:14 is considered normal. Therefore, the quality of the fuel-air mixture depends on the correct readings of the flow meter.

The high-quality work of the DMRV depends largely on the cleanliness of the air filter. Therefore, if symptoms of a malfunction of the DMRV appear, before making repairs, the air filter should be checked first. The flow meter is usually beyond repair. If it is defective, then it is changed to new device. But its cost is quite high, so you should first make sure that the causes of the problems are in the sensor, not in other machine malfunctions.

The signal for diagnosis is the following symptoms of a malfunction of the DMRV:

There are other symptoms of a sensor malfunction. For example, it may have cracks in the corrugated hose that connects the throttle to the sensor. If the engine stalls, there may be a power problem or damaged wiring. This is a signal to check the wiring. If a malfunction is found, the electrical system of the machine must be repaired.

In addition to the above signs, it is necessary to diagnose the level of the sensor signal.

A low signal level can mean the following:

Do not draw conclusions about the malfunction of the mass air flow sensor, relying only on the symptoms listed above. A complete diagnosis of the engine and machine should be carried out, since signs of a flow meter breakdown may appear when other devices malfunction. Then you need to repair these devices in order to restore the performance of the car.

Check and repair

There are five ways to check the MAF.

Method number 1. Checking the performance when the air flow meter is turned off. The method consists in disconnecting the sensor from the vehicle's fuel system and checking the system's performance without it. To do this, disconnect the connector of the device and start the engine. Without DMRV, the controller receives a signal to switch to emergency operation. It prepares the air-fuel mixture only based on the throttle position. If the car moves “faster”, does not stall, then the device is faulty and needs to be repaired or replaced.

Method number 2. Flashing. If the standard firmware has been changed, then it is not known what reaction the controller has in it in case emergency. In this case, try to put a 1mm thick plate under the throttle stop. Turnover should increase. Now you need to pull the chip from the air flow meter. If a power unit will continue to work, then the cause of the malfunction is the firmware.

Method number 3. Install a known-good device and start the engine. If after replacement it began to work better, the motor does not stall, then the device needs to be replaced or repaired.

Method number 4. Troubleshooting by visual inspection. For this you need Phillips screwdriver unscrew the clamp holding the air collector corrugation. Then you need to disconnect the corrugation and inspect internal surfaces corrugations of the air collector and sensor.

They must be free of oil and condensation, surfaces must be dry and clean. If you do not monitor the air filter and change it rarely, then dirt can get on the sensitive element of the sensor and cause it to break. This is the most common malfunction. Traces of oil may appear in the flowmeter when elevated level oil in the crankcase, and also if the oil deflector is clogged ventilation system crankcase. If necessary, clean the surfaces with special cleaners.

Method 5. Checking the DMRV with a multimeter. To do this, turn on the tester in the mode in which the constant voltage is checked. The limit value for measurements should be set to 2V.

Sensor pinout:

1. The wire yellow color located closer to the windshield. It serves as an input for the signal from the flow meter.
2. White-gray wire - sensor voltage output.
3. The black/pink wire leads to the main relay.
4. The green wire is used to ground the sensors, that is, it goes to ground.

Wires may be different colors, but their location is unchanged. To check, you need to turn on the ignition, but do not start the car. The red probe from the multimeter must be connected to the yellow wire, and the black one must be connected to ground, that is, to the green wire. We measure the voltage between these two outputs. Multimeter probes make it possible to connect without disturbing the insulation of the wires.

On a new device, the output voltage is in the range from 0.996 to 1.01 V.

During operation, this voltage gradually increases and its value can be used to judge the wear of the flowmeter:

• if the sensor is in good condition, the voltage is from 1.01 to 1.02 V;
• in a satisfactory condition - from 1.02 to 1.03 V;
• the sensor resource ends if the voltage is in the range from 1.03 to 1.04 V;
• a near-death state is indicated by a value ranging from 1.04 to 1.05, if there are no contraindications, then you can continue to use the sensor;
• if the voltage exceeds 1.05 V, the MAF needs to be replaced.

Diagnosis of the DMRV is not difficult and can be done by hand.

If there is dirt on the sensor, you can clean it yourself. You can use WD-40 to clean it. To clean the DMRV, you must first remove the pipe from it, and then dismantle the device itself. Inside the device there is a mesh and several wires - sensors.

They need to be sprayed with a cleaning agent and cleaned. Then let the liquid dry. If dirt remains, then the procedure should be repeated. With the same tool you need to clean the pipe. It must be free of dirt and oil stains. After replacing the air filter, all parts must be returned to their place. After the cleaning procedure at 80%, you can restore the device to work, the error about the low level of the sensor signal disappears (the author of the video is Alexey Romanov).

Flushing the sensor will help avoid costly repairs.

Replacing the DMRV

To replace the sensor with your own hands, you need to prepare a curly screwdriver and a key to "10".

The replacement procedure consists of the following steps:

Thus, if the machine stalls, has all the signs of a breakdown of the DMRV, then before starting its repair, you should check the level of its signal, it should not be low, perform a complete diagnosis of the machine and repair all faulty components and parts.

It is important to have your car checked regularly and on time. Maintenance, then parts and assemblies will last longer.

Video "Checking the MAF with a multimeter"

This video from the Simple Opinion channel demonstrates how to check the MAF with a multimeter.