Air flow sensor failure will lead to unstable engine idle speed and poor acceleration. This paper introduces how to detect the air flow sensor.

1) When the engine is running, unplug the plug of the air flow sensor. If the fault disappears, it means that the signal of the air flow sensor has deviation and is not damaged. The electronic control unit always controls the fuel injection according to the error signal with deviation.

How to detect the fault of air flow sensor

Bearing remover

Because of the imbalance of the mixing ratio and the abnormal combustion of the engine, there will be unstable engine speed or poor power. When the plug of air flow sensor is pulled off, the electronic control unit will immediately enter the failure protection function if it does not detect the air intake signal, and replace the air flow sensor signal with the throttle position sensor signal, so that the engine can continue to work with the replacement value. Unplug the plug of the air flow sensor, and the fault disappears. It just shows that the signal before unplugging is incorrect, and the signal after unplugging is correct, so the fault disappears.

2) The dynamic signal voltage is measured at the signal end of the plug. Under idle condition, the standard voltage is 0.8-1.4v; when accelerating to full load, the voltage signal can be close to 4V. If it is not in the range, the air flow sensor itself may be damaged. In some cases, it is also caused by dirt, which can be cleaned.

3) When the engine is running, unplug the plug of the air flow sensor. If the fault persists, the main reason is that the air flow sensor is damaged (the relevant circuit may also cause the fault); the engine control unit cannot receive the signal of the air flow sensor, and the electronic control unit confirms that the signal of the air flow sensor is poor, which leads to the failure of the protection function. At the same time, it will code the fault Memory.

4) When the engine is running, pull off the plug of air flow sensor, the fault phenomenon slightly changes. It indicates that the air flow sensor is good. Before unplugging the air flow sensor plug, the electronic control unit controls according to the signal of the air flow sensor. The fuel injection quantity is accurate and the engine is in good condition. When unplugging the air flow sensor plug, the engine control unit controls according to the signal of the throttle position sensor. The fuel injection quantity is slightly different and the engine condition is similar Yes, slightly worse.

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