General information
The hot-wire air flow sensor consists of a heat-sensitive film sensor, a housing and a measuring channel (hybrid sensor element). The principle of measuring air mass flow by this type of sensor is based on the fact that a change in the air flow passing through the sensor causes a change in the amount of heat transferred from the surface of the film sensor element (film) to the air flow. As a result, the temperature of the hot-wire sensor changes and its resistance changes.
Based on the sensor signal, the engine control unit determines the required fuel supply (basic open time of the fuel injector) and the ignition timing.
The mass air flow sensor generates pulses by successively opening and closing the circuit that supplies 5 V power from the engine control unit.
Type 1. |
Type 2. |
Troubleshooting Guide
1. If the engine stalls occasionally, start the engine and try shaking the MAF sensor wiring harness. If the engine stalls after this, check for poor contact in the MAF sensor connector.
2. If the MAF sensor output signal is registered to be different from zero when the ignition is turned on (key position "ON") and the engine is not running, then the MAF sensor or the engine control unit may be faulty.
3. If the engine is idling (even if the MAF sensor output voltage is not normal), the cause is usually one of the following faults:
- a) Violation of the normal flow of air through the mass air flow sensor, disconnection of the air duct or clogging of the replaceable air filter element.
- b) Incomplete combustion of the working mixture in the cylinder, malfunction of spark plugs, ignition coil, injectors and violation of compression.
- c) Defective intake manifold (air leak).
4. Even if there are no signs of a faulty mass air flow sensor, check that it is installed correctly (air flow direction).
Note:
- On a new car (mileage less than 500 km), the readings of the mass air flow sensor will be higher than the actual air flow by approximately 10%.
- It is recommended to use an accurate digital voltmeter when performing checks.
- Before starting the check, it is necessary to warm up the engine so that the coolant temperature reaches 80-90°C.
Checking the sensor
1. Measure the voltage between terminals "2" (signal) and "1" (ground) of the connector on the sensor side under the specified conditions when the connector is connected.
- a) Check the voltage when the ignition switch is turned to the "ON" position and the engine is idling.
- Nominal value: 0.5V
- b) Check the voltage when the engine is running at 2000 rpm.
- Nominal value: 1.0 V
2. If the measured voltage differs from the nominal value, replace the mass air flow sensor.