Flow meter maintenance

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How to repair the car air flow meter? The ECU of the electronic control fuel injection system has a fault storage function, which summarizes the working conditions of various sensors and actuators and compares them with fixed programs stored in the computer. If the error exceeds the specified range, it will be treated as a fault storage. Maintenance personnel can know the specific fault situation through a fault reader (detector). There is a similar fault resolution situation, such as a contradiction between the air flow meter signal and the oxygen sensor signal. How will the computer output it? Fault 1: The Jetta 20V engine has unstable idle, weak driving, and black smoke. After a basic troubleshooting, it recurred a few days later. Testing process: The computer displayed a temporary malfunction in the air flow meter. Despite replacing the air flow meter, the malfunction persisted. Using the V.A.G1551 fault diagnosis instrument, the entire vehicle data block was tested and found to be normal. However, during the specific testing of the air flow meter circuit, it was found that the resistance value of the air flow meter signal line was too high, with a normal value of 0.5 Ω and an actual value of 3.6 Ω. The real reason is that there is a virtual connection in the circuit. After handling the wiring harness plug, the fault was eliminated. Fault analysis: This type of fault belongs to a special fault, but it is often encountered in actual maintenance and relatively difficult to solve. At that time, we found a problem: the signal line of the air flow meter is located at the corner of the plug, which is prone to position failure during the production process, resulting in poor contact. In other plugs, the corresponding positions are also worth our attention. In addition, as a crucial component, the failure rate of the air flow meter is very low. When the computer prompts for its failure, we should be cautious. Fault 2: Jetta 20V has unstable idle speed, emitting black smoke under partial load, and sometimes stalling during gear shifting. Detection process: The fault stored in the computer is an air flow meter fault, but the specific detection of the air flow meter circuit shows that the situation is normal. The fault still persists after replacing the air flow meter. After replacing the computer, the cold car works normally, but the fault still persists after heating the car. At this point (using the V.A.G1551 fault diagnosis instrument), the entire vehicle data block was checked again, and it was found that the voltage change frequency of the oxygen sensor in the 7th group and 2nd zone of the 08 data group was slow. Normal changes occur 20-30 times per minute, with an average of only 5-6 times, indicating a malfunction in the oxygen sensor. Repair result: Replace the oxygen sensor and troubleshoot. Fault analysis: This fault is caused by the contradiction between the air flow meter signal and the oxygen sensor signal in the computer. In fact, it is due to the inaccurate oxygen sensor, resulting in incorrect adjustment. However, from the results, it is the same as the serious deviation of the air flow meter signal, which caused the oxygen sensor to be unable to adjust. Here, the computer prioritizes important signals such as the air flow meter signal. As long as we can correctly understand the computers fault prompts, the problem will not be difficult to solve. This malfunction can be understood as: from the malfunction related to the ai

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