The mass air flow sensor is used to determine the amount of air entering the engine cylinders

The signals from the sensor are sent to the engine control unit and are one of the parameters that determine the duration of fuel injection by injectors - the amount of fuel depends on the amount of air at any given moment.

The main element of the sensor is a platinum filament heated up to 150 °C during operation.

As engine intake air passes through the sensor housing, the filament cools down, and the sensor electronics constantly strive to maintain the filament temperature at 150 °C.

Electrical power spent on maintaining the temperature of the thread is a parameter by which the engine control unit determines the duration of the electrical pulse applied to the nozzles.

The degree of cooling of the platinum filament depends not only on the amount, but also on the temperature of the passing air, determined by a thermal compensation resistor, which accordingly corrects the signal supplied by the sensor to the control unit.

To provide the ability to adjust the amount of carbon monoxide in the exhaust gases at idle, the electronic module has a variable resistor, with a screw of which you can manually change the value of the signal supplied by the sensor to the electronic control unit, thereby changing the duration of the pulse applied to the injectors, and hence the amount of injected fuel.

In order to clean the platinum filament from contamination, the electronic module periodically applies an increased voltage to it, causing it to heat up to 1000 °C. In this case, all deposits are burned.

If the sensor fails, the engine control unit turns on a backup program that ensures engine operation with slightly different, but acceptable power and consumption characteristics.

At the same time, the indicator lamp in the instrument cluster lights up.

Disconnect the wire from the "negative" terminal of the battery.

Disconnect connector 1 from mass air flow sensor 3.

Loosen the clamps, disconnect the air supply hoses 2 and remove the sensor 3.

Replacing the mass flow sensor GAZ-2705

Install the new sensor in reverse order.

Mass flow sensor test

Remove the mass air flow sensor.

Connect a voltmeter to pins "2" and "3" of the sensor connector.

Supply 12 V DC to pins 1 and 5 (“+” to pin “5”, and “–” to “1”). In this case, the voltmeter should show a voltage of 1.3–1.4 V.

Then briefly close contacts "4" and "5" between each other.

At the same time, the voltmeter should show a voltage of about 8 V, and the platinum thread should become red-hot.

If at least one of these conditions is not met, replace the sensor.