Fault phenomenon of air flow meter | How to determine if the air flow meter is broken

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Is the gas mass flow meter user-friendly?

2. What are the symptoms of a broken car air flow meter? The signal from the air flow meter is the core data of the engine electronic control system. Once this sensor malfunctions, it will have a significant impact on the normal operation of the engine. The car will have a malfunction indicator light on, and the engine will experience idle shaking, poor acceleration, stall after starting, and other phenomena due to inappropriate air-fuel ratios in various operating conditions. With the industrial development of our country, there have been many changes in the types of air flow meters. According to the development of the times, air flow meters are divided into four categories: L-type, D-type, hot wire type, and hot film type. The structure of the first generation L-type air flow meter was the simplest, but of course, there are no more models in use now. The second type is the D-type air flow meter, which is an upgraded version of the first generation air flow meter and can improve its performance. The third type is the hot wire air flow meter, which is widely used. Its biggest feature is that it can use the characteristics of a thermistor to maintain a constant temperature of the hot wire, ensuring stable accuracy in measuring intake air volume. The structure and working principle of the hot film air flow meter are similar to those of the hot wire type, mainly improving the disadvantage of the hot wire being dirty (causing inaccurate measurement values) after prolonged use. This is currently the most widely used flow meter. The structure of the air flow meter is shown in the following figure. It uses a Wheatstone bridge composed of a thermistor, platinum wire, and two precision resistors internally. The engine ECU provides current to the power transistor to heat the platinum wire to a certain temperature. When air flows through the temperature sensor and platinum wire, it will take away the heat from the platinum wire. At this time, the ECU will increase the voltage flowing through the Wheatstone bridge, which is proportional to the amount of intake air passing through the intake pipe. The ECU calculates the fuel injection amount based on this value, thereby changing the air-fuel ratio ratio. The original air flow meter that causes malfunctions can generate various faults during use, which can affect the normal use of the air flow meter. The main reasons for the malfunction of the air flow meter are:

1. Fault in the air flow meter circuit. In the normal operation of the engine control system, all the data provided by the sensors must be correct and reliable. When the liquid level of a sensor circuit fails, causing the output signal to exceed the normal range, the engine ECU cannot recognize the signal normally. For example, the maximum voltage output by the sensor is 5V. If the voltage transmitted to the ECU is 12V, the ECU cannot correctly know what information the sensor is transmitting. The ECU stores this fault information in Simultaneously output fault codes in the memory. The voltage output by the air flow meter is between 0.2-4.9V. When the voltage signal received by the ECU is not within this range multiple times, a relevant fault code will be reported. However, occasionally the voltage is abnormal, and the engine ECU will not pay attention to it. This may be caused by accidental contact between the lines or vehicle bumps during driving. If the fault code P0100 is outpu

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