What is a mass air flow sensor (MAF) and what does it come with?

Correct operation of the engine depends on the performance of many devices, in particular, we are talking about sensors. In particular, we are talking about the mass air flow sensor (MAF), which is equipped with all modern engines. We will tell you more about what a mass air flow sensor is, what types of regulators there are, and what the operating principle of the device is, below.

Why do you need a mass air flow sensor

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

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

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

How can you bypass the regulator?

DMRV decoy circuit

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

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

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

Why does the mass air flow sensor fail?

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

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

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

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

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

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

How to quickly determine that the sensor is faulty?

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

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

How to understand that the mass air flow sensor has failed

To put it bluntly, the sensor sends a signal to the ECU about the amount of air passing to the injector and the “brains” determine how much fuel needs to be supplied. In the most common engine designs, the proportions of fuel and incoming gas are strictly observed and are approximately equal to 1:14. When the mass air flow sensor fails, malfunctions, and mixture formation is disrupted, which radically changes the dynamic characteristics of the power unit.

If there is a malfunction in the operation of the unit, a sharp change in the behavior of the car occurs. Only by observing the behavior of the machine can you understand that the unit requires intervention. Common signs of a bad mass air flow sensor include:

1. Reduced transport dynamics. An incorrectly formed fuel mixture burns poorly in the cylinders, which negatively affects the acceleration and smooth running of the car.
2. The engine does not start or stalls spontaneously. When the sensing element falsely triggers or sends an incorrect signal to the on-board computer, an incorrect amount of fuel may be supplied at start-up. In this case, the engine floods or chokes. A similar action can occur during idle.
3. The check engine light on the dashboard lights up. A light indicator can inform the motorist about a breakdown long before serious problems arise. Fine electronics are configured to read the smallest false data and transmit a pulse to the main equipment.
4. Fuel consumption has increased. When a car initially takes 10-12 liters per hundred, and then consumption sharply increases to 15-16, you should immediately check the serviceability of the sensor. Also, some cars suffer from the fact that they can empty part of the tank at one moment, and then behave as usual.
5. The speed of the power plant fluctuates. This is possible if the sensor does not respond correctly when you press the gas pedal or the engine is running quietly. The danger lies in the fact that when driving, the car can suddenly accelerate without pressing the gas pedal.

If such problems are detected, official dealers recommend immediately contacting specialists for a routine inspection of the machine.

What is he responsible for?

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

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

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

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

Negative consequences of improper operation of the mass air flow sensor

If the mass air flow sensor does not work correctly, negative factors may appear. Among the most common ones stand out.

1. Critical excess consumption of gasoline/diesel. The part may transmit too strong an impulse to the electronics, which provokes an intense supply of fuel into the combustion chamber.
2. Unstable engine operation during acceleration and idling. The car starts to jerk and may stall unpredictably.
3. Accelerated wear of the catalyst and particulate filter. Improper mixture formation leads to an increase in soot in the exhaust, which negatively affects the cleanliness of the exhaust.
4. Critical wear of the piston group. When the mixture burns incorrectly, the temperature regime of the engine is disrupted. Such problems subsequently lead to jamming of the piston group with all the ensuing troubles.

What does the malfunction lead to?

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

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

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

Checking the air flow sensor for serviceability

There are two methods for determining failure. The first is to go to the master. The second involves searching for the problem yourself. If everything is clear with the service station, some difficulties may arise during home repairs. Home renovations usually happen in stages and consist of the following steps.

Visual inspection

Here you should unscrew the air supply line after the filter and inspect the inner surface of the pipeline. It should be clean and dry here. If there is dirt, drops of moisture or other contaminants, they can clog the sensor hole, causing it to malfunction.

This can happen if the air filter has not been changed for a long time, or the oil sump of the crankcase ventilation system has broken.

The problem can be resolved by thoroughly cleaning all surfaces and blowing out the sensor nozzle.

Disconnect flow meter

If you disconnect the sensor from the on-board system, the ECU goes into emergency mode and supplies fuel based solely on the throttle position. If the machine starts working normally, the sensor is definitely faulty.

Firmware check

If you have a diagnostic scanner, you can connect it to the device and check for errors in the firmware or reinstall it. More precise manipulations with the software depend on the machine model.

Reading errors

Most modern cars have a built-in self-diagnostic function. After switching the dashboard to service mode, the display will display a list of alphanumeric codes indicating the cause of the breakdown.

If the standard system fails to recognize a failure, you can resort to an external scanner. The device is connected through the standard output of the on-board network, and with its help, complete diagnostics are performed. It is noteworthy that an external scanner allows you to accurately determine the cause of the breakdown and the place where it should be looked for.

Replacing the sensor

The simplest and most reliable way to check the machine is to replace the sensor with a known good one. The principle is to install a new device and check the stability of the engine with it.

Calling

The multimeter is switched to DC measurement mode with a maximum voltage of 2 Volts. Depending on the type of sensor and vehicle manufacturer, the pinout of the contact group may vary significantly. Therefore, before the procedure you will need to find service information for the required car model. The operating voltage range of the sensor is also preliminarily studied (the nominal parameters of individual specimens may differ slightly).

Signs of malfunction of the DMVR

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

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

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

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

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

How to replace the mass air flow sensor - general provisions

Depending on the make of the car and the modification of the power plant, the principle and sequence of actions may differ significantly. In most cases, the sensor is a separate structural element with its own power supply and a separate signal transmission line. In more complex motors, the mass air flow sensor acts as part of a complex module and is changed as a block.

The following instructions are for informational purposes only and show the basic sequence of actions.

1. Place the vehicle on wheel chocks or the handbrake.
2. Open the hood and remove the positive terminal from the battery.
3. Depending on the design of the unit, unscrew the sensor from the mounting socket or loosen the clamp securing the air duct.
4. Disconnect the MAF contact group terminal from the plug connector.
5. Installing a new device is performed in reverse order.

The main factor when performing the operation is careful adherence to cleanliness. The finest sensor settings can be lost when exposed to moisture or dust. Also, the master will require extraordinary accuracy. There are extremely sensitive elements inside the part; they are easily damaged by accidental impact or shaking.

Separately, it should be taken into account that you can perform the operation yourself only with complete confidence in your own abilities. If in doubt, it is recommended to contact a qualified specialist.

How to clean the mass air flow sensor

Over time, the sensitive element of the sensor can become covered with inorganic microparticles and a film formed from oil fumes, which impairs the correct air readings. The control unit program corrects the distorted sensor signals up to a certain point, but at the critical limit of the permissible range it turns on the emergency light, reporting an error in the fuel system. In addition, symptoms of a malfunction of the mass air flow sensor appear in the form of failures and fouling of the spark plug electrodes with soot.

The factory does not recommend cleaning the air flow sensor with various types of liquids, especially solvents and carburetor cleaners. You can clean the sensor by spraying the measuring element with alcohol. Cleaning the sensor with alcohol will not cause harm. Before turning the ignition key, make sure that the air path of the sensor is clean and, if foreign objects are present, remove them with tweezers or any tool suitable for this purpose.

Breakage Prevention

To avoid failure of the mass air flow sensor, you should follow some recommendations.

1. Change the air filter in a timely manner. Clogged cells often allow dust particles to pass through, which can disrupt the correct perception of the situation.
2. Promptly inspect the rubber and plastic elements of the line for cracking, holes, and loose fasteners.
3. Use the sink carefully. If water gets into the engine compartment, the liquid can get into the electronic units, causing them to malfunction.
4. Avoid deep discharge of the battery. The electronics of some cars can “revolt” when the voltage in the on-board network is critically reduced.
5. Use only original spare parts for repairs. When installing counterfeit or low-quality parts, the machine manufacturer cannot guarantee that they will work correctly.

Nissan Almera

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

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

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

Procedure:

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

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

How to troubleshoot?

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

Replacement

The controller changes like this:

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

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

Disconnecting the power supply from the flow meter

Removing the device from the seat

Cleaning

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

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

VAZ 2110 air sensor pinout diagram

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

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

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

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.

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.