The gauge of a mass airflow - how to check? DFM sensor

The mass air flow (MFR) sensor is attached to the air filter and determines the amount of air that it passes through. The correct definition of this indicator depends on the quality of the combustible mixture. Malfunctions of the mass air flow sensor will immediately affect the operation of the engine.

Symptoms of damage

At the first signs of engine failure, do not panic, rush to the store and take a new DMR. It can be assumed that the mass air flow sensor is damaged. How to test its operation? First, you need to listen carefully to the car. He himself will indicate that the DMRV sensor is faulty, and will behave as follows:

• the computer will issue a "Check Engine" error;

• power will decrease;

• fuel consumption will increase;

• the engine will not start properly;

• The speaker will decrease.

What should I do if the mass air flow sensor is not working correctly? How to check his condition?

Option 1: Disconnect

With the engine switched off, disconnect the connector from the DMRV. The device will turn off, the controller will go into emergency mode, and the fuel mixture will be prepared taking into account the current position of the throttle. On the transition to this mode, the engine will again report, it must keep a speed of more than 1500 rpm. The final conclusions about the MFR malfunction can be made if, during the movement, you realize that after the sensor has been turned off, the speaker has improved. Note: The ECU Modification I-7.2 and M-7.9.7 after disabling the DMRV will not increase the engine speed.

Option 2. Firmware

It is possible that the computer has already been modified by firmware, then it is not entirely clear how it will behave when using the option above. In this case, the mass air flow sensor may also not work correctly. How to check this? We take a plate 1 mm thick and insert it under the stop of the flap. After the engine speed has risen , disconnect the terminal from the DMRV. If the engine continues to operate, then the cause of the fault in the computer, namely in the steps of PXX. They do not respond to the emergency mode without the DMRV.

Option 3: Multimeter Diagnosis

This option is suitable for diagnostics of Bosch sensors with indices: 0 280 218 004, 0 280 218 116, and also 0 280 218 037. On the tester, set the measurement limits of 2V, in the constant voltage mode. Marking of wires (orientation from the passenger compartment):

• Signal input - yellow;

• Sensor power supply - gray-white;

• Ground (minus) - green;

• To the main relay - pink-black.


The color of the wires is specified for most models, colors may vary, but the value of the leads is the same.

Measurement procedure

After switching on the ignition, without starting the engine, we perform a scan. The red probe of the device is connected to the yellow wire of the DMRV, and the black one to the green one. So we conduct a voltage measurement and fix it. Comparing the received indications with recommendations of the manufacturer that will allow to judge about working capacity of the device. The new DMRV has a voltage of 0.996-1.01 V.

Device performance parameters depending on voltage:

1.01-1.03 - the sensor is operational;

1.03-1.04 - it is functional, but the sensor resource is almost exhausted;

1.04-1.05 - the resource is exhausted, if there are no signs of a malfunction, it can be exploited, but it's time to acquire a new one;

1.05 and more - defective, replacement is required.


To check the mass air flow sensor, you can check the "voltage from the sensors" parameters from the on-board computer .

Option 4: Visual inspection

Using a screwdriver, unscrew the clamps, taking away the corrugation, examine the sensor and the corrugation. All surfaces should be dry without oil deposits and condensation. Causes of pollution DMRV:

• contaminated air filter;

• the oil level is higher than normal;

• the mesh filter, ventilation systems are clogged.

Eliminating the causes of pollution of the DMRV, it is necessary to correct the consequences, and this will require the cleaning of the mass air flow sensor. Using a key for 10, unscrew the sensor mounting bolts, detach it from the air filter. The sensor should have a rubber ring to prevent raw air from sucking in. If there is no or is not in place, then the input grid of the device in question will be in dust. This may cause the sensor to malfunction. Sequence of installation:

• the device is fitted with a rubber band;

• the sealing skirt is checked;

• the sensor is installed in the filter housing.

Replacement procedure

After switching off the ignition, remove the plug from the sensor. Loosen the clamps, detach the intake air inlet. Next, unscrew the sensor and remove it from the filter body. To unscrew it, you will need a key to 10. After inspection, the question arises again if the mass air flow sensor is faulty, how to check its efficiency. Evaluating the diagnostics of the device, do not immediately acquire a new one. It should be noted that the cost of DMRV varies from 1500 to 2000 rubles. But you can simply eliminate the pollution and spend a maximum of 200 rubles.

Means for removing contaminants

In order to clean the DMRV qualitatively, it must be removed, the order of removal has already been described earlier. There is a grid inside the device. It is equipped with 2-3 sensors, in the form of small wires. During operation, the parts become dirty, which leads to malfunction. To give a second life to the device, it is necessary to clean the mesh and sensors, for this purpose the carburettor cleaner is suitable. By spraying the product, we wash the dirt from the inside of the DMRV. Complete elimination of contaminants can occur not from the first time, it is necessary to repeat the procedure. All subsequent spraying should be carried out after the agent dries. When cleaning the sensor, it is worthwhile to inspect the condition of the nozzles - if there are contaminants, remove them. The use of a carburettor to remove contaminants shows that 8 out of 10 devices start working in the correct mode after treatment. But in some cases, you have to buy a new MFR sensor.


Now, the verification of the DMRV on its own can be considered complete. And the questions about whether the mass air flow sensor is correct, how to check its condition, can be responded with a 100% guarantee to the SRT by conducting a diagnostic examination using special equipment.

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