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A Honda front 1. 8L car with a mileage of about 63 thousand km, the owner reflects that the car will fail to shift the automatic transmission, fault diagnosis: 1) first use HDS to read the automatic transmission fault code, showing P0718: the intermittent failure of the input shaft speed sensor and P0722: the output axis speed sensor has no signal. Input. 2) disconnect the two sensor plug according to the fault code, and then open the ignition switch, check its line 1 terminal and the voltage of 5V, 2 terminal, and 3 terminal voltage to 5V, indicating that the line of the two sensor is normal, but the phenomenon of the two sensors is damaged at the same time, may be an illusion, not more. Change the sensor, so look for other possible fault points. 3) after the use of HDS to remove the fault code, the road test is carried out to find that the vehicle has accidental normal shift, but the shift has a sense of vibration. It may be an intermittent fault. After the vehicle runs for half an hour, the fault reappears. Using HDS to read the trouble code, there is no fault code, so that people are puzzled. 4) when the engine is in the idle state, the oil pressure test is carried out on the automatic transmission, and the oil pressure is too low, but the maintenance personnel have replaced the automatic transmission oil and the ATF filter when the owner reflects the car before it is repaired in the 4S store. According to the low oil pressure analysis, the main reason is the hydraulic torque converter, ATF pump, regulating valve, hydraulic torque converter one-way valve or ATF filter block, but the ATF filter has been replaced, so the other components are checked one by one, and the unidirectional valve of the hydraulic torque converter is found to be invalid and the cause of the failure is found. 5) after changing the torque converter assembly, the vehicle will be tested, the automatic transmission will work normally and the trouble will be eliminated.