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A 2007 mildi win 2.3L car with a mileage of about 180 thousand km, matching the 6 speed manual transmission of Ai Xin. User response: the vehicle stalled on the transmission. When the engine was running normally, the engine was idling and the speed did not change significantly. Because the car is in the field, had to find a local small repair factory repair, the transmission is not carefully checked after loading, and after driving, the shift has a shock, and the fault indicator light is not bright. Because the car had just been repaired before, it could not find its clue for a while, and entered the transmission system by car V30. Enter the transmission control module, TCM power supply is normal, communication lines are all normal. The gear shift from P to D is normal. There is no obvious impact. Check TCM internal failed to find fault code, PCM is also normal, temporarily not good to judge the cause of failure, customarily reprepared for the normal data flow of TCM, and then the road test. Put the bar to the D position, starting forcefully and shifting smoothly, when switching from D to P gear, it is found that the shift is serious impact, N, R, P, any stop fault is consistent and the fault light does not light, the other gear is only the S block and the 5 gear normal. Fault analysis: after the 1. test, the engine trouble code is retrieved to show "transmission control unit failure". Clean up the fault code and no longer appear. 2. read the TCM fault code, showing "P2738", that is, "the pressure solenoid valve F voltage is too low". 3. read the relevant data stream and find that all solenoid valves are inconsistent with their reference current (the data flow has been noted before). 4. the initial judgement is that the voltage of the solenoid valve is too low to work properly, and the solenoid valve can not be opened normally, resulting in too high oil pressure and impact. Generally speaking, the F solenoid valve voltage is too low, mainly for the following reasons: 1) TCM damage. 2) there are problems with TCM to F solenoid valve lines. 3) the resistance of the solenoid valve is too high. Troubleshooting because the S and 5 gears are normal, the initial judgment is TCM damage. After changing the new TCM, it is found that the stop lamp or the F solenoid valve is checked, the transmission is dismantled, and the resistance value of the solenoid valve is 6.6 omega and 13.5 Omega respectively. After consulting the relevant manual, it is found that the value is not abnormal. You have to unplug all the plugs and check the oil circuit boards. During the inspection, it is found that the F solenoid valve is in bad contact, and after the fastening of the solenoid valve, the trouble is eliminated. Hydraulic automatic control system is usually composed of oil supply, manual gear selection, parameter adjustment, shift timing control, shift quality control and so on. The oil supply part adjusts the output oil pressure of the oil pump to the prescribed value according to the throttle opening and the position of the selector lever, thus forming a stable working hydraulic pressure. In the liquid controlled hydraulic automatic transmission, the parameter adjustment part mainly includes the throttle pressure regulating valve (the throttle valve) and the speed controlled pressure regulating valve (also known as the governor). The throttle pressure regulating valve enables the output hydraulic pressure to reflect the throttle opening; the speed control valve regulates the output hydraulic pressure to reflect the speed of the vehicle. The pressure adjusts the solenoid valve, one adjusts the main oil pressure, the other adjusts the hydraulic twister to lock the oil pressure. The 2 oil pressure also controls the shift valve body in the oil plate, and there is a bad work, which will cause the shift impact. The failure of this case is not very difficult, but the two rework has caused a lot of trouble to the diagnosis. Fault summary: with the development of modern automobile technology, automatic transmission has been applied more and more widely. But compared with the traditional manual shift mechanical transmission, there are many problems such as complex structure, difficulty in inspection and maintenance. In the course of using the automatic transmission, once the abnormal condition or malfunction occurs, it is necessary to carry out dynamic check to identify the cause of the failure. In addition, after the automatic transmission is completed, it is necessary to carry out dynamic check when it is on hand to make sure that it is in good condition. The use of the fault detection instrument can greatly improve the efficiency of fault diagnosis, especially when the two diagnosis, if it can be timely reprepared for the data flow, for the practitioners of the repair industry, it is a good habit.