What is the mass air flow sensor, a valuable structural part of the car. This indicator is necessary for the electronic device that controls the motor. To monitor the correct amount of air being supplied. In this case, it is the air that is combustible for the fuel mixture. The sensors come in different designs, but their failure will lead to a malfunction of the main operating process of the car.
DMRV what is it
In modern cars, engines are equipped with gasoline injection devices. Therefore, it is necessary to use special measuring sensors - mass air flow sensors. Modern air flow indicators are installed on diesel and gasoline engines.
Functions and purpose of the sensor
Nowadays, cars use two types of fuel supply: with distributed injection, fuel is supplied to the inlet pipe, and with direct injection, fuel is supplied directly into the chamber. In both situations, the operation of the vehicle depends on the correct functionality of the mass air flow sensor. Several years ago it worked on a mechanical basis, but now there are no moving elements and the sensor is manufactured on a hot-wire type.
The mass air flow sensor is suitable for any type of engine, and the functionality of the valve of the exhaust gas removal and neutralization complex is concentrated on it.
As experienced drivers like to say, the engine does not function in only two ways - there is nothing to burn or nothing to ignite.
Using an air flow sensor, the control unit receives information about the volume of gases entering through the intake channel, which regulates the required amount of fuel to produce the mixture.
Symptoms of a malfunctioning mass air flow sensor and consequences
It is not at all necessary for an ordinary car owner to thoroughly know how the mass air flow sensor works. But the ability to recognize the symptoms of its malfunction helps to prevent possible problems with the operation of the fuel injection system in advance. If the flow meter sends incorrect calculations to the ECU, this can cause the formation of either a lean or over-rich air-fuel mixture. In the first case, there will be a significant decrease in the power of the power unit, in the second - excessive fuel consumption.
The most common symptoms of a malfunctioning mass air flow sensor are:
the engine operates stably only at a certain speed level;
in normal operation there is a significant increase in fuel consumption;
there are difficulties starting the engine;
spontaneous engine stops - that is, it stalls;
Check Engine diode lights up on the instrument panel;
reduction in vehicle acceleration dynamics.
Of course, the cause of a stalled motor can be not only the sensor, but also problems with the power supply. Therefore, it is checked first, and only then is the sensor subject to diagnosis. Its performance is determined by the voltage level, measured in Volts. Moreover, this method is applicable both for flow meters with thread and for film meters, which supply a digital signal to the control unit. Therefore, this signal in new models of film sensors can also be determined by measured built-in means, which in the event of a malfunction will generate an error code.
If the signal level of a filament flow meter is low, this can be caused by a number of factors:
the electronic engine control unit is faulty;
a break in the electrical connection circuit of the flow meter;
signal wires are incorrectly connected or broken;
open circuit mass;
sensor is not connected.
And yet, one should not draw final conclusions about what the DMVR is and why it does not cope with its task based on the above points. Ideally, it is advisable to conduct a complete diagnostic of the engine, and not necessarily the entire machine. After all, very often the cause of a drop in power and spontaneous engine shutdown is a simply clogged air filter. However, there are indicators that allow us to say with almost one hundred percent probability that the cause of the problems is the flow meter
DMRV - what is it
The air flow indicator is designed to inform the owner that air is moving into the engine, because oxygen is a combustion catalyst for a flammable composition. Having received data from the air flow sensor, the fuel system prepares a correctly formed combustible mixture and ensures complete combustion of the fuel. The device located in the fuel inlet path includes two resistors. Which are performed in all sorts of variations.
In one embodiment, the element is exposed to a passing air mass. With a change in its intensity, the temperature of the thread decreases, as does the immanent resistance. In another embodiment, the resistor is not affected by the air mass. Based on the difference in resistance of the two elements, the volume of oxygen required by the motor for operation is calculated.
The principle of operation of the mass air flow sensor
At its core, mass air flow sensors are equipped with two sensitive thermistors in the form of a very thin heating metal wire. A direct current is supplied to them to heat them to the required number of degrees. One wire is in the air mass, due to the influence of air it is cooled. The second is provided with protection in the form of a screen. Thanks to this, the air cools the second thread less. Based on the difference between these two resistors, the air volume required for the smooth functioning of the engine is determined.
air supply sensor
Some MAF indicators have a built-in thermometer that shows the temperature order of the incoming air mass. This allows for more accurate calculations. Also, instead of metal threads, ceramic heating elements and thin films can be used. One way or another, they work according to the same system - the temperature difference between two components is taken into account - open and protected.
How to check the air flow meter
The process of checking the air flow meter is simple and can be done in several ways. Let's look at them in more detail.
Disabling the sensor
The simplest method is to turn off the flow meter. To do this, it is necessary to disconnect the power wire suitable for the sensor (usually red and black) with the engine turned off. After this, start the engine and drive the car. If the Check Engine warning light lights up on the dashboard, the idle speed exceeds 1500 rpm, and the car's dynamics have improved, then it is highly likely that your mass air flow sensor is faulty. However, we recommend that you perform additional diagnostics.
Checking with a scanner
Another diagnostic method is using a special scanner to identify errors in car systems. Currently, there is a wide variety of such devices. More professional models are used at service stations or service centers. However, for the average car owner there is a simpler solution.
It consists of installing special software on a smartphone or tablet with the Android operating system. Using a cable and adapter, the gadget is connected to the car's ECU, and the mentioned program allows you to obtain information about the error code. To decipher them you need to use reference literature.
Popular adapters:
Adapter ELM327
- 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.
The most common error codes:
- P0100 - mass or volumetric air flow sensor circuit;
- P0102 - low signal level at the input of the mass or volumetric air flow sensor circuit;
- P0103 - high signal level at the input of the mass or volumetric air flow sensor circuit.
Using the listed hardware and software, you can not only search for air flow meter errors, but also make additional settings for the installed sensor or other components of the car.
Checking the flow meter using a multimeter
Checking the mass air flow sensor with a multimeter
Also popular among car enthusiasts is the method of checking the flow meter using a multimeter. Since the most popular mass air flow sensor in our country is BOSCH, the verification algorithm will be described specifically for it:
- Turn on the multimeter in DC voltage measurement mode (abbreviated as DC). Set the upper limit so that the device can detect voltages up to 2 V.
- Start the car engine and open the hood.
- Find the air flow meter directly. It is usually located on or behind the air filter housing.
- The red lead of the multimeter must be connected to the yellow wire on the sensor, and the black lead to the green one.
- If the sensor is working properly, then the voltage value on the multimeter screen should not exceed 1.05 V. If the voltage is significantly higher, it means that the sensor has completely or partially failed.
We provide you with a table that shows the value of the received voltage and the state of the sensor.
| Voltage value, V | Sensor status |
| 0,966…1,01 | Voltage value on the new mass air flow sensor |
| 1,01…1,02 | Good condition of the sensor |
| 1,02…1,03 | Average condition |
| 1,03…1,04 | Sensor life is coming to an end |
| 1,04…1,05 | Very bad condition |
| Over 1.05 | The sensor needs to be replaced urgently |
Visual inspection and cleaning of the air flow meter
If you do not have a scanner or appropriate software at hand 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 there are often situations when dirt, oil or other process fluids get into its body. This results in errors in the data produced by the device.
For a visual inspection, the first step is to dismantle the flow meter. Each car model may have its own nuances, but in general the algorithm will be approximately as follows:
- Turn off the car ignition.
- Using a wrench (usually 10), disconnect the air hose through which air is supplied to it.
- Disconnect the wires listed in the previous paragraph from the sensor.
- 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 good condition and not broken or oxidized. Also check for dust, debris and process fluids both inside the housing and directly on the sensing element. Their presence may cause errors in the broadcast readings.
Accordingly, if these contaminants are detected, it is necessary to clean the housing and the sensitive element. To do this, it is best to use an air compressor and a rag ( with the exception of the film flow meter, it cannot be cleaned or blown with compressed air ).
Alcohol (ethyl or methyl) is well suited for this purpose, but it is better to use specialized MAF cleaners. Their composition does not corrode the sensitive element of the sensor. If you are using alcohol, you can draw it into a syringe and pour it over the flow meter under slight pressure. With professional sprays everything is simpler - just open the lid of the can and spray over the entire surface of the sensor. After this, the air flow sensor should dry out - leave it in a ventilated place for about 20-30 minutes.
Perform the cleaning procedure carefully so as not to damage its internal elements, especially the threads.
Results
Finally, we will give some more tips on how to extend the life of the air flow meter. First, change your air filter regularly. Otherwise, the sensor will overheat and produce incorrect data. Secondly, do not allow the engine to overheat and make sure that its cooling system is operating normally. Third, when cleaning the air flow meter, perform this procedure carefully. Unfortunately, most modern mass air flow sensors cannot be repaired, so if they fail completely or partially, they need to be replaced accordingly.
Types of mass air flow sensors, features of their design and operation
The earliest prototypes of the air flow sensor were based on the principles of changing the resistance of a resistive component. A plate in the mechanism body bent under the force of the air mass. The more the plate was bent, the more the resistance changed. The control system received measurements of the amount of fuel mass that the engine could burn.
At the moment, a pair of metal threads is used, heated to the same temperature. The operating principle of this sensor is described above. The most recent models use platinum-coated silicon wafers. It is this plate that measures the intensity of the air flow.
Currently, only two subtypes of the Sensor are used:
- resistor threads,
- sensitive film component.
They work according to fundamentally the same scheme - they measure the amount of air mass going into the engine. Both types of indicators have their positive and negative sides.
Concept and design of mass air flow sensor
The controller that controls the amount of incoming fuel must have a decoding from the control unit about the amount of air moving through the manifold. Such readings are given by the mass air flow sensor (MAF). The quality of the fuel-air mixture, and therefore the operation of the power unit, depends on the accuracy of the device readings.
The mass air flow sensor is a small device. It is located between the air pipe that goes to the throttle body and the air filter. The photo shows where the device is located.
Location of the flow meter in the engine compartment
Its task is to determine the amount of air that comes from the filter. The operating principle of the device is based on changing the temperature of a metal layer that is welded onto a ceramic layer or a thin platinum wire from the flow of incoming air.
The device consists of a plastic body, which is a pipe with a diameter of 60 mm, at both ends of which there are protective grilles. Inside the housing there is a sensitive element of the device (platinum wire or plate).
The mass flow sensor has the following wire pinout:
- yellow indicates an incoming signal;
- green is used for grounding;
- black and pink goes to the main relay;
- white-gray – for voltage output.
The photo shows a diagram of the distribution of flowmeter wires and their interpretation.
DMRV operation diagram
Kinds
Modern devices for cars are constantly being improved, this also applies to the air flow meter. There are several types of it depending on the principle of operation.
The first flow meters were vane meters. They were based on a pitot tube. The main element is a softly fixed thin plate (scapula).
Scheme of operation of the blade device
The operating principle is similar to a throttle valve. Due to the flow of incoming air, the plate begins to bend. This circuit includes a potentiometer that measures how much the plate is bent, at which point the resistance of the potentiometer changes. Changing the resistance readings on the potentiometer gives an interpretation for the control unit of the volume of incoming air. In modern hot-wire devices, the function of a heat exchanger is performed by platinum wire.
Plate sensors have become widespread. This flowmeter uses thin platinum plates as a heat exchanger. They are heated by the incoming energy. One of the plates is control, the other is working. The job of the sensor is to ensure that both plates have the same temperature. This is done as follows: thanks to the flow of incoming air, the working plate is cooled. Since the temperature of the reference and work plates must be the same, more current is supplied to the work plate if its temperature is lower.
Plate air flow meter
The third type of flow meter is film, it uses sensors with film meters. The working elements of the film sensor are silicon plates coated with platinum. Film mass air flow sensor appeared on the market not so long ago and has not yet become widespread.
Sorry, there are no surveys available at this time.
Advantages and disadvantages of fuel mass flow sensors
| Mass air flow sensor with thread | Mass air flow sensor with film element | ||
| pros | minuses | pros | minuses |
| Simplicity of design | Inaccurate readings | Accuracy | Impossibility of repair |
| Unpretentiousness | Does not meet Euro 3 and 4 standards | Environmental friendliness | Lack of self-cleaning |
| Not afraid of pollution | Meets Euro-3 requirements | Excessive sensitivity | |
| Self-cleaning capability |
Why does the air flow sensor become unusable?
The control system receives information from the fuel mass consumption indicator that air is reaching the injection devices. Then the control unit identifies the volume of fuel mass that is supplied according to these data. The most common proportion of fuel and air mass is 1 to 14. When the indicator breaks, the formation of this composite mass is disrupted and this affects the dynamic characteristics.
Adverse consequences of incorrect operation of the Fuel Flow Sensor
If the DMVR breaks down, you may notice changes in the behavior of the car. The main features are:
- Reduced car dynamics: the car accelerates poorly, its movement becomes jerky.
- The engine may stall spontaneously or fail to start. In the event of a false operation or an incorrect impulse being sent to the control unit, an excess or incomplete amount of fuel may be supplied at the start. It is clear that in this case the motor does not have enough power or there is too much of it, as a result of which it runs the risk of being flooded or simply stalling.
- The “Check Engine” error light on the dashboard starts to light up. By paying attention to this signal in time, you can avoid serious problems.
- Fuel consumption increases. If a car initially spends 10-12 liters per 100 km, and then suddenly starts to “eat” 15-20 liters of gasoline/diesel fuel, this is a reason to check the mass air flow sensor. Some cars with such a malfunction can empty the tank in a short time, and then return to normal consumption.
- Power unit vibrations. This happens when the car engine is idling or when the pedal is pressed. The threat to the car lies in a sudden increase in speed without the influence of the driver.
If any of the above described signs are detected, you should immediately contact the service for preventive maintenance of the car. In addition, the machine can only operate at low or only high speeds, which will negatively affect the condition of the engine.
Signs and causes of malfunctions
If the flow meter partially fails, the driver will notice one or more of the situations listed below. 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 (when accelerating, the engine “fails” when you press the accelerator pedal);
- significant excess fuel consumption;
- The Check Engine light on the dashboard lights up.
The listed symptoms may also be the result of other malfunctions of individual engine components, however, among other things, it is necessary to check the operation of the air flow meter. Now let's look at the reasons why the described malfunctions occur:
Flow meter restoration
- Natural aging and sensor failure . This is especially true for relatively old cars that have an original flow meter installed.
- Motor overload . Due to overheating of the sensor and its individual elements, it may produce incorrect data for the ECU. This occurs due to the fact that when the metal is significantly heated, its electrical resistance changes, and, accordingly, the calculated data for the amount of air passing through the device.
- Mechanical damage to the flow meter . It can be the result of various actions. For example, damage when replacing the air filter or other components close to it, broken contacts during installation, and so on.
- Moisture getting inside the housing . The reason is quite rare, but it can occur if a large amount of water gets into the engine compartment for some reason. This may cause a short circuit in the sensor circuit.
As a rule, the flow meter cannot be repaired (except for 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 carburetor cleaner.
How to replace the mass air flow sensor - general provisions
The engine type and car make have an impact on the sequence of service, including changing the air flow indicator. For the most part, the mechanism involves a separate part under the hood of the car that is attached to the air purification filter. There are also indicators included in the complex module. In such a situation, replacement is only possible for the entire block.
The procedure for changing the mass air flow sensor is as follows:
- Place the car on anti-roll bars or on the handbrake.
- Raise the hood and disconnect the negative terminal of the battery.
- Unscrew the indicator or loosen its fasteners.
- Disconnect the sensor terminal from the connector.
- Install a new sensor, performing all steps in reverse order.
During operation, it is necessary to carefully maintain cleanliness so as not to disrupt the fine settings of the device. If dust or moisture gets in, they can get lost, and therefore even a new indicator will not work correctly.
