Definition
The air flow sensor, also known as an air flow meter, is one of the key sensors in the EFI engine. It converts the flow of inhaled air into an electrical signal and sends it to an electronic control unit (ECU). A sensor that measures the flow of air to the engine as one of the basic signals to determine fuel injection.
Type
There are many types of air flow sensors for electronically controlled gasoline injection systems. General air flow sensors can be classified into blade (wing plate) type, measurement core type, hot ray type, hot film type, Karman scroll type, etc. according to the type of structure.
Detection method
Blade type (wing plate type) air flow sensor
- Measure resistance value
First, turn off the ignition switch, disconnect the power cord of the battery, and then disconnect the wire connector of the wing type air flow sensor. Use a multimeter to measure the resistance between the terminals. The resistance value must meet the standard value. Otherwise, the air flow sensor is damaged and needs to be replaced.
- Measure the voltage value
First plug in the inlet connector of the air flow sensor, then turn the ignition switch to the “ON” gear and use a multimeter to measure the voltage between the VC and E2 terminals and between the VS and E2 terminals. The measurement result must meet the standard value. If not, the air flow sensor is damaged and needs to be replaced.
- Measuring work output signal
Unplug the injector harness, start the engine, or use only the starter to rotate the engine and use a multimeter to measure the voltage between the VS and E2 terminals. The voltage should decrease as the blade opening gradually increases. If not, it means air. The flowmeter is damaged and needs to be replaced.
Karman scroll type air flow sensor
- Measure resistance value
First, turn off the ignition switch, disconnect the power cord of the battery, and then disconnect the wire connector of the air flow meter. Use a multimeter to measure the resistance between the THA and E2 terminals of the air flow meter. The measured value must conform to the standard value. If not, the air flow meter is damaged and needs to be replaced.
- Measure voltage value
Connect the air flow meter input connector first, then turn the ignition switch to the “ON” position and use the multimeter to check the voltage values between the terminals listed in the table. It must meet the standard value requirements. Otherwise, the air flow meter is damaged and must be replaced.
- Measuring work output signal
Disconnect the injector harness, start the engine or use the starter alone to run the engine, and use an oscilloscope to measure the pulse between the E1 terminal and the KS terminal. There must be a standard pulse waveform, otherwise the air flowmeter is damaged and must be replaced.
Hot film type air flow sensor
- Turn off the ignition switch, disconnect the air flow meter input connector, and use a multimeter to measure the resistance between the 3terminal and the grounding point of the vehicle body. It should be 0Ω.
- Turn the ignition switch to “ON” and use a multimeter to measure the voltage between terminals 2 and 3 of the air flow meter. It should be the battery voltage. If there is no voltage or the reading deviation is too large, check the circuit. Check whether the voltage between the 4 and3 terminals should be around 5V, otherwise it means there is a problem with the cable between the ECU and the air flow sensor or ECU. If there is static wind when stopping, check that the ground voltage of terminal #2 is about 14V, otherwise it means that the circuit between the air flow meter and the fuel pump relay is faulty. The voltage between #3 and #5 terminals should be about 1.4V when there is no load. As the engine speed increases, the voltage at both ends should continue to rise, and the maximum value is about 2.5V, otherwise the air flow meter should be replaced.
- Turn off the ignition switch and remove the air flow meter. When there is no wind, the voltage between terminals 3 and 5 should be about 1.5V. Use a blower to blow cold wind at the inlet of the air flow meter, and then slowly move the blower backward. As the distance increases, the voltage value between terminals 3 and 5 should gradually decrease, otherwise the airflow should be replaced by counting.
I hope that the relevant information we shared about the air flow sensor can help everyone. Any interests, welcome to contact our VW Air Flow Sensor manufacturer.
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Post time: Nov-24-2021