Malfunction: a Shanghai Buick Regal car, using LB8 engine and 4T65E automatic transmission. Because most of the components in the automatic transmission are damaged, they are replaced by a "4T65E" automatic transmission with the same type. A few days after the factory, there was a driving fault. Fault diagnosis: for the road test, there is a fault phenomenon described by the owner. So the fault detector was first detected by the fault detector. The fault code read was P1811, which means "maximum adaption and long shift". After removing the fault code, read the trouble free code again. A road test was carried out on the car, and no driving and punching were found. After a week's use of the car, the above faults appeared again, and the frequency increased. Once again, using fault detector to detect, the fault code read is still P1811. Troubleshooting: again on the road test, running less than 5 km, the above failure, read the fault code, or P1811, then clear the fault code, and then the road test, the above failure again. Consulting the raw materials of the Buick sedan car, according to the 15 reasons of the maximum fit and long shift, we decided to replace a group of solenoid valves first, and then the road test was carried out, and the fault still existed. Then change the distribution valve assembly, the failure is still. Remove the body and disintegrate the body and find out some valves in the valve body, so the valve body and a group of solenoid valves are replaced, but after the assembly is assembled, the fault remains, the fault code is read, or P1811. After consultation, I suspect that there is something wrong with the mechanical part of the automatic transmission. I have decided to consult with the Beijing distributor. An automatic transmission assembly assembled by a Beijing dealer has been tested after loading, and the fault still persists. Before the road test, connect the fault detector to track detection and record the relevant data for analysis. During the operation of the car, the fault detector showed the shift time varied from 0.35S to 1.22 S. After running for about 15 km, there was a continuous 2 burst phenomenon at a speed of about 40 km / h at less than 100m. Continue to refer to the original information of Buick Regal car, and introduce the "P1811 fault code", which means the most suitable and long shift. The condition of the fault code in the run of the fault code is the fitness value. When the 1 - 2, 2 - 3, 3 - 4 adaptation unit has reached the limit value, or 1 - 2, 2 - 3, 3 - 4 shift time exceeds 0.65S, the fault code P1811 is stored in a stroke, it is a C type fault, once the fault code is stored, The power system control module (PCM) will take the following action: the power system control module (PCM) does not light the fault indicator; the power system control module directs the maximum pipeline pressure; the power system control module freezes the adjustment value; when the condition of setting the fault code is set, the power system control module records operation. State, and store the information as a fault record. " According to the reminder of the maintenance data, it is felt that the oil pressure should be detected at shifting time, but the work failed because of the damage of the oil pressure gauge joint. Further consultation and unification of the thought, according to the original factory information about the fault code P1811 maximum appropriate value and shift time too long, decided to disassemble the two automatic transmission separately, and assemble the high quality executive components of the two table into an ideal automatic transmission, in accordance with the original structure of the factory, one piece A contrastive assembly. After the assembly is finished, the automatic transmission oil (ATF) of the original plant model is added, the fault detector is connected to the road test, the result is still still, the fault code is still P1811. At the time of the helpless, it was decided to consult Beijing. It was found that there were two kinds of transmission sprockets for the automatic transmission, one is the main and the driven sprocket is 35 teeth, the other is 32 teeth and the driven sprocket is 37 teeth. As a result, the automatic transmission in Beijing was disassembled, and the result was that the main and driven chain wheels were all 35 teeth. Then the road test is carried out to detect the speed ratio of the input shaft and the output shaft of the automatic transmission. The 1 gear is 1:0.80, the 2 is 1:0.95, the 3 is 1:1.22, and the 4 is 1:1.28. Because the 3 transmission of the automatic transmission is direct block, the speed ratio of the main and driven shaft should be 1:1, and the abnormal ratio is actually 1:1.22. Immediately, the automatic transmission on the vehicle is lifted down. The result of the dismantling test is that the number of main and driven chain teeth is 35 teeth. Then the automatic transmission of the original car was opened and checked. The number of teeth of the main and driven sprockets were 32 teeth and 37 teeth respectively. The sprocket and the transmission chain of the original automatic transmission were installed together on the automatic transmission to carry on the road test, and the failure phenomenon disappeared. The fault detector indicates that the speed ratio of the input shaft and the output shaft of the automatic transmission is 1:0.86, 1:0.95, 1:1 and 1:18 respectively. The above fault is completely eliminated.