How to detect the malfunction of the air flow sensor?
A malfunction of the air flow sensor will cause unstable engine idling and poor acceleration. This article describes how to detect an air flow sensor.
1) When the engine is running, unplug the air flow sensor. If the fault disappears, it means that the signal of the air flow sensor is biased and not damaged. The electronic control unit always performs fuel injection control according to the biased error signal.
Due to the misregistration of the mixing ratio, the engine will not burn properly, and the engine speed will be unstable or underpowered. When the air flow sensor plug is unplugged, the electronic control unit will immediately enter the fail-safe function when it cannot detect the intake air signal, and replace the air flow sensor signal with the throttle position sensor signal, so that the engine continues to work at the substitute value. Disconnecting the air flow sensor plug, the fault disappeared, which precisely indicates that the signal was incorrect before the plug was unplugged, and the signal was correct after the plug was unplugged, so the fault disappeared.
4) When the engine is running, unplug the air flow sensor, and the fault phenomenon changes slightly. The air flow sensor is good. Before the air flow sensor plug is unplugged, the electronic control unit controls it according to the air flow sensor signal. The fuel injection is accurate and the engine is in good working conditions. When the air flow sensor plug is unplugged, the engine controls. The unit is controlled according to the throttle position sensor signal. There is a slight difference in the fuel injection amount, and the engine operating conditions are relatively poor.
3) When the engine is running, unplug the air flow sensor. If the fault persists, the main reason is that the air flow sensor is damaged (the related circuit will also cause the failure); the engine control unit cannot receive the air flow sensor signal. The control unit confirms that the signal of the air flow sensor is bad, enters the fail-safe function, and stores the fault code in the memory.
2) The dynamic signal voltage is measured at the signal end of the plug. Under idle conditions, the standard voltage is 0.8 to 1.4V; when it is accelerated to full load, the voltage signal can approach 4V. If it is not in this range, the air flow sensor itself may be damaged. In some cases, it may also be caused by dirt, and cleaning is sufficient.
If you want to know more, our website has product specifications for the air flow sensor, you can go to ALLICDATA ELECTRONICS LIMITED to get more information