What does dmrv mean. The main features and device of the DMRV

By controlling the operation of an automobile engine, the electronic unit acts according to the readings of a group of main sensors. These include a meter for the amount of air drawn in by the intake manifold through the open throttle. Receiving this data, the controller increases or decreases the fuel supply, achieving the optimal ratio of the components of the combustible mixture. The failure of the flow meter significantly impairs the performance power unit up to the impossibility of further movement. Therefore, it is advisable for novice drivers to study the signs of a sensor malfunction. mass flow air (abbreviated as DMRV).

Flowmeter design

Knowing the design of the air sensor, you will quickly understand the principle of its operation and understand why a faulty meter cannot be repaired, but only replaced. It is not difficult to find the device - it is built into the air duct connecting the filter - air flow purifier with the throttle valve. The exact location depends on the make and model of the car.

Hot-film or hot-film gauges are installed on most vehicles in use. The difference is in the design of the sensing element, the principle of operation remains unchanged. The anemometric flow meter is a case, where 2 platinum threads are placed - measuring and reference. How does the DMRV work in a car:

1. The controller supplies power to both threads. As they heat up, they change resistance in the same way.
2. When the motor is running, the first thread is washed by the air passing through the throttle and cooled. The stronger air flow, the more intense the cooling.
3. The electronic unit captures the difference in resistance between the measuring and reference threads. Having made the calculation, the ECU determines the mass of the passing air and sends the appropriate amount of fuel to the injectors.

Reference. In modern cars with turbocharged engines, mass flow sensors have been replaced with absolute pressure meters (MAP) - more reliable devices with long term services. Manufacturers began to complete new atmospheric engines with similar products.

Film measuring device operates on the same principle, only instead of threads, platinum-coated ceramic elements are used. That is why it is quite possible to check the DMRV, but it is impossible to repair it. A burnt thread or a damaged coating cannot be replaced, only the entire product.

The consequences of a sensor failure

When, for various reasons, the sensor fails or gives incorrect readings, the controller changes the operation algorithm. He begins to prepare the air-fuel mixture, focusing on the throttle position meter and lambda probe. Due to the lack of data previously received from the DMRV, the electronic unit "does not know" about the actual amount of incoming air and cannot mix it with gasoline in optimal proportions.

Thanks to the transition of the controller to emergency operation, it is possible to determine the main symptoms of a malfunction of the DMRV:

• on the dashboard the driver's control unit turns on the Check Engine light display, indicating a malfunction in the fuel supply or ignition system;
• idling is unstable - it either rises to 1500 rpm, then drops to zero (the engine stalls);
• "on a cold" engine starts with great difficulty;
• incorrect preparation of a combustible mixture causes an increase in fuel consumption, regardless of driving conditions and operating mode;
• there is a decrease in the power of the power unit and frequent causeless jerks on the go.

Note. The inclusion of the Check Engine indicator does not give the driver specific information about the nature of the breakdown. The inscription calls for diagnosing engine systems using a computer connected to the service port. In this way, you can check the performance of the DMRV and other sensors in a service station.

Indirectly, a malfunction of the flow meter is indicated by the appearance of black smoke from exhaust pipe. If on vehicle there is no on-board computer and it is impossible to track the instantaneous consumption of gasoline, it is worth unscrewing 1-2 candles from any cylinders and inspecting the electrodes. A layer of black soot will confirm the excessive enrichment of the mixture due to the emergency operation of the electronics.

If the motorist does not respond to the above problems and continues to operate the car, then he will have to face bigger troubles. Constant re-enrichment of the fuel mixture will quickly render the spark plugs unusable, the combustion quality will deteriorate, the load on the cylinder-piston group will increase, and wear will accelerate significantly. The prospect is gloomy - the repair of the power unit.

Causes of problems

The air flow meter becomes unusable for the following reasons:

• a lot of dust and dirt gets on the measuring elements, because the car owner rarely changes the air filter;
• on heavily worn engines, gasoline and oil vapors penetrate into the DMRV through the crankcase ventilation pipe;
• a hole in the corrugated duct, from which dust is sucked;
• accidental damage due to unskilled repairs;
• broken wires connecting the sensor connector to the controller.

In addition to these reasons, there is also a natural wear of the device. The resource of the new DMRV is 50-250 thousand km, depending on the brand and origin of the car.

Diagnostics in garage conditions

The above symptoms also occur with other breakdowns, for example, failure of the oxygen sensor or throttle position. In all such cases, the electronic unit acts in the same way - it goes into emergency mode for preparing an air-gasoline mixture. Hence similar consequences.

To check the mass air flow sensor without instruments, follow a series of simple steps:

1. Open the hood and disconnect the connector from the MAF.
2. Start the engine and monitor the idle speed. The controller must raise the crankshaft speed to 1500 rpm and hold them stably. If the idle continues to “float”, the flow meter is most likely good.
3. Make a test run for a short distance, observing the behavior of the car. If the motor started to work even worse, then the problem lies elsewhere.

This technique does not allow you to accurately determine the "culprit" of the problems, especially when there are several of them. For example, the lambda probe failed in parallel. It is necessary to carry out a more accurate diagnosis - check the MAF with a multimeter according to the following instructions:

1. Switch the multimeter to voltage measurement mode. Open the hood and look for the sensor connection block.
2. Connect the red wire from the device to the input signal contact (usually colored yellow). Connect the second clamp with black insulation to the green conductor.
3. Turn on the ignition and record the voltmeter readings.

A voltage in the range of 1–1.03 V indicates that the sensor is fully operational. If signs of emergency mode are monitored while driving a car, it is worth checking the other meters that affect the fuel supply.

Readings of 1.04–1.05 volts indicate that the platinum elements of the sensor are decently worn out, you should prepare to replace the DMRV. A value of 1.06 V or more indicates that the air mass meter ordered to live for a long time. You need to purchase a new meter and install it on the duct instead of the old one.

If, as a result of the diagnosis, you received average readings, the sensor will not hurt to clean it. Do not try to get inside the DMRV with various brushes - a special liquid is commercially available for this purpose, which washes away dirt from the air mesh and measuring elements.

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

DMRV is located in the air duct near 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 failure 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 the power unit continues 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 with 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 the inner surfaces of the corrugation 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 rarely change it, 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 yellow wire, and black 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;
• the 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 regularly pass the inspection of the car and perform maintenance on time, then the 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.

"Mass air flow sensor (DMRV) - what is it and what is it for?" - a question of interest to many novice motorists. The short answer is: the mass flow sensor is important element ICE control systems with a microprocessor ignition system (ECU). Its task is to measure the amount of air entering the engine cylinders. Based on the MAF readings, the engine controller calculates the amount of fuel that the injector should supply. The usual location of the flow meter is after the air cleaning filter and before the throttle valve.

Why do you need a DMRV

If you try to set something on fire in a chamber where oxygen is completely absent, then nothing will come of this venture. To maintain the combustion process, an oxidizing agent is needed, in our case O2. In internal combustion engines, it is used as an oxidizing agent. atmospheric air, which contains oxygen. It is not enough just to burn the fuel - it is necessary that it burns without residue. The correct proportion of the fuel-air mixture is the key to maximum engine performance. Quantity required air and fuel for gasoline engines defined as 14.7 to 1 (by weight). The fuel-air mixture of this composition is called stoichiometric.

In modern engines, fuel dosage control is entrusted to a computer. In order to accurately determine the amount of fuel that an injector needs to inject, it needs data on the amount of air that has entered the engine intake manifold. DMRV and is responsible for obtaining this data.

Operating principle

The action of the sensor is based on the measurement of the electrical power, which is necessary to maintain the temperature of the heating element located in the housing. The ram air cools the element in the sensor, and the internal combustion engine controller seeks to maintain the temperature by supplying an electric current. The more air passes through the sensor, the more power is required to maintain its temperature. The power is converted into a signal that the controller of the control unit receives. Based on the received signal, the ECU calculates the amount of fuel that the injector should supply to the intake tract. The amount of air passing through depends on the angle to which the throttle valve is open.

Sensor design

The mass air flow sensor consists of two parts - a housing and a measuring element. Housing DMRV round section has rubber o-rings at the ends. They are needed in order to prevent air leakage bypassing the air filter.

The measuring element can be of two types:

• with wire heating element
• with foil heating element

Both in the case of the wire and in the case of the film, the material is platinum. This explains quite high cost DMRV.

Mounted in the measuring element circuit diagram, which generates and sends a frequency-pulse signal to the motor controller.

Symptoms

The service life of the flowmeter is not regulated by the manufacturer, and depends on the following factors:

• the amount of deposits on heating element;
• supply voltage stability.

Malfunctions of the DMRV electrical circuit are recorded by the controller and recorded in the computer memory in the form of error codes. They can be considered a tester for engine diagnostics.

Signs that the sensor is faulty may include:

• uneven engine idling;
• failures in the operation of the engine when changing the position of the throttle;
• increased fuel consumption;
• spontaneous engine stop when shifting gears in motion.

When an error occurs in the operation of the DMRV, the engine control unit switches to emergency operation mode. In this case, the controller uses data from the throttle position sensor (TPS) and the crankshaft position sensor to calculate the air volume. It is not possible to accurately calculate the volume from the readings of these sensors, so fuel consumption increases dramatically.

Repair or replacement

The sensor is very sensitive to deposits on the heating element. If they were the cause of the incorrect signal, you can try to wash them. To clean the thermocouple, use ethanol. But flushing in most cases does not give a long-term effect. After a while, it will still need to be replaced with a new one. In order for the sensor to serve for a long time, it is necessary to carefully monitor the condition of the air purification filter and change it in time.

It happens that the incorrect operation of the motor is caused by air that is sucked through the seal after the flow meter. Then to restore normal operation enough to restore its tightness.

In most cases, when a DMRV malfunction is detected, only replacing it with a new one will help. In this case, it is necessary to purchase the part exactly the same as it was installed earlier. Sensors for different systems engine controls are not interchangeable. Even externally indistinguishable flow meters from the same manufacturer, designed to work with different engine ECUs, produce a different output signal. When purchasing a new sensor, you must ensure that the number of the new sensor matches the number of the old one.

When engines are running internal combustion, which are equipped with modern cars, the combustion of the fuel-air mixture occurs, for the formation of which, as you might guess from its very name, it is necessary to mix the fuel with air, and in strictly defined proportions. Accordingly, the systems that are responsible for the formation of this substance, at each moment of the operation of the power unit, must accurately “know” the consumption of each of its components. The value of this indicator for one of them helps to determine the mass air flow sensor (DMRV). It should be noted that it is present in the design of only injection motors, and if drivers notice signs of a malfunction of the DMRV, then they should check it and, if necessary, replace it.

What does a mass air flow sensor look like on a car?

This important sensor is located directly behind the engine air filter, or more precisely, just between it and throttle assembly. It is arranged so finely that it allows you to measure with high accuracy the flow rate of only that air that is well cleaned of mechanical impurities.

During operation, the DMRV transmits electronic system engine control signals that are processed and interpreted as the volume of air that is supplied to form the fuel-air mixture. For normal operation of the power unit, the volume ratio in it of liquid fuel (gasoline, diesel fuel) and air should be close to 1x14. If this proportion is violated, then either a significant loss of engine power occurs, or an excessive consumption of fuel (by the way, these are the main signs of a malfunction of the DMRV). The information received from the sensor that determines the mass air flow helps to avoid this.

The DMRV measures the amount of air that per unit time enters the fuel rail. It transmits this data to the ECU, which instantly calculates the amount of liquid fuel that must be supplied to form the mixture, and gives the appropriate “orders” to the engine devices responsible for this. Thus, if, for example, you press the accelerator pedal, then more air immediately begins to flow in, the DMRV instantly determines this, sends data to the computer, which increases the supply of gasoline or diesel fuel in the appropriate proportion. If the amount of air decreases, then the volume of liquid fuel supply also decreases.

In terms of design, there are three types of such sensors that are actively used:

• Pitot tube based;
• With hot-wire meters;
• With film gauges.

DMRVs built on the basis of the Pitot tube are considered obsolete and are not used in the newest engine models. They are so-called vane flow meters, the main elements of which are plates connected to potentiometers and softly fixed on the axes. Changing their position under the influence of air flow, they act on a potentiometer, which changes its electrical resistance.

Mass air flow sensors with hot-wire type meters are quite expensive, although they are very effective. They are equipped with special heat exchangers, consisting of two platinum threads, which are heated by passing electric shock. One of them is blown by an air stream, the second remains a control one, and according to the difference in the current passing through them, the ECU calculates the amount of air entering to form the fuel mixture. DMRV with film meters are considered the most modern. According to their principle of operation, they are almost similar to hot-wire anemometers, only they use not platinum filaments, but ceramic elements with platinum coating.

The main symptoms of a malfunction of the mass air flow sensor

A malfunction of the DMRV, as noted above, leads either to over-enrichment or to depletion of the fuel mixture with gasoline or diesel fuel, which negatively affects the operation of the engine and can lead to its serious damage. Most often, DMRV malfunctions are associated with clogging of the air filter: the air is not cleaned well, and the mechanical particles contained in it enter the sensor, which is the cause of its breakdown. It should be noted that mass air flow sensors are non-repairable devices, and if they fail, they have to be replaced with new ones.

Practice shows that the main signs of a malfunction of the DMRV are as follows:

• A Check Engine error appears, which indicates that the signal level of this sensor is very low;
• The engine consumes more fuel than usual;
• The power unit does not start well, its power decreases, it starts to stall;
• The car does not accelerate well;
• The engine runs either at high or low speed.

Of course, all the signs can also appear with other car malfunctions, but in any case, if at least one of them is found, this is a good reason to visit the station. Maintenance. However, you can check the DMRV for malfunctions on your own, without contacting service station specialists.

The most obvious and early sign of a malfunctioning or failing MAF is a flickering dashboard light. However, many malfunctions can cause this effect. Therefore, it is necessary to test the car's on-board computer to make sure that this is due to the mass air flow sensor.

As the DMRV plays important role in maintaining the proper balance of air and fuel inside the engine, engine failure can cause a range of powertrain performance problems. These may include low mileage after refueling, shaking when the engine is running, problems starting the engine, rattling or noises. These signs can appear much earlier than the DMRV reaches a critical state and the indicator on the dashboard lights up indicating a breakdown.

Sometimes the mass air flow sensor becomes dirty and therefore starts to work poorly. Although the air passing through the MAF cleans it, microscopic debris accumulates on it. internal surfaces. Large accumulations of contaminants lead to damage to the device. In this case, the part can be returned to its original condition by simple cleaning. However, it is worth remembering that the sensor is a very delicate device and from careless handling it can become completely unusable.

There are other malfunctions of the DMRV. For example, if everything is in order with the device itself, the corrugated wire that connects it to the on-board computer may become unusable. As a result, the signal will be sent to the central processor with a delay, which will negatively affect the operation of the engine. To make sure that it works, you need to ring the wire or another similar device.

Diagnostics

The mechanic can check the on-board computer at service center. You can also do it yourself using a digital scanner for diagnosis. These scanners are available at most auto parts stores. While they all work a little differently, they are generally designed to connect to an OBD-II vehicle diagnostic port. Therefore, all scanners can read data from a computer.

After verification, the scanner will show one or more alphanumeric codes, which can be found in the directory. More advanced models display brief information about the code on the screen. If, after decryption, it becomes clear that the malfunction is related to the DMRV, then it must be replaced or repaired. It is worth noting that mass air flow sensors are rarely repairable, as they are easier and cheaper to simply replace.