M-DCT double clutch automatic vehicle for automatic transmission, locking clutch failure will have a great impact on the vehicle. The common faults of the clutch are as follows: the clutch can not be engaged, can not be separated, unproperly joined and slipped. There are many kinds of malfunctions, so it is very important to master its working principles, characteristics and methods of analyzing faults. The maintenance personnel used to go to a Ford 1996 Wind Star car. When the vehicle is moving at high speed and high speed, the vehicle is jitter, giving people the feeling that the engine is jitter and the seat is the same. According to the car owner, the fault has been repaired many times in other repair plants, and a large number of spare parts have been replaced on the engine, but the failure phenomenon has not improved at all. First, a road trial was made, and the vehicle was jitter regularly between 40 80km / h. The engine was tested first, but no fault was found. The consideration may be caused by other factors at this time. Then a computer detector reads the data flow, and it is found that when the lock clutch (TCC) joins, especially when the platform is 40% - 60%, the vehicle will be jitter. The fault is therefore caused by poor combination of TCC. But which part is caused by the bad end of the platform? The fault may lie in the parts of the electric control, hydraulic and mechanical systems. Of course, there are some special situations, such as when the throttle is closed, the brake is applied, the speed speed is accelerated or the gear shift, the temperature of the oil is lower than 60 C and the gear is too high and the gear is under the 3 gear, for these times, the locking clutch is not joined. The engagement and separation of the locking clutch is controlled by the computer (PCM) through the electromagnetic clutch of the locking clutch (TCC). The computer analyzes the signal of the throttle position sensor, the speed sensor, the turbine shaft sensor, the gear shift time and the brake switch, provides the duty ratio signal to the TCC solenoid valve, changes the opening of the TCC solenoid valve, and controls the movement of the clutch. For the work of TCC, the computer is monitored by the speed of the engine and the rotational speed of the turbine shaft (input shaft). When the lock clutch does not work, the engine speed should be more than 200 - 300r / min of the turbine shaft speed; in the locking clutch engagement process, the speed difference between the two should be gradually reduced; when the lock clutch is fully engaged, the speed difference between the two should be basically zero. Therefore, by observing the difference between engine speed and turbine speed (input shaft speed), we can judge the state and quality of the clutch. When judging some failures that can not be joined or separated, it is also possible to connect the transmission detector (a testing tool that can control the work of the solenoid valve), disconnect the control of the transmission by the computer, control the work of the clutch solenoid valve, and judge the fault of the control part or the executive part. The fault is divided. If the manual failure of the solenoid valve of the manual clutch still exists, it is clear that the electric control part has no problem. If the fault is on the electronic control part, we should check whether the signals provided by the sensors that affect the TCC work are normal, and then check whether the PCM can work correctly according to the signal of each sensor, and finally check the connection of the wire is good. The fault of hydraulic part can be judged by measuring the oil pressure. So the transmission of this car was tested by hydraulic pressure. In the road test, there was no fluctuation and abnormal oil pressure when the TCC joint jitter occurred. To further determine whether there is any fault in the hydraulic part of the transmission, the valve body is folded down and mounted on the test template, and compressed air is used for testing. The results show that all hydraulic valves and valve bodies of TCC work well, and the possibility of failure of hydraulic parts can be eliminated. As for the mechanical part, because it can not be disassembled and decomposed, it can only be determined by excluding other faults. Through the above several aspects of detection and analysis, maintenance personnel to determine that the fault may only be on the mechanical part, that is, torque converter locking clutch. It is necessary to remind the maintenance personnel that the torque converter should be paid attention to the cleaning problem of the torque converter in the maintenance of the transmission, so as to avoid the foreign body entering the damaged torque converter and the locking clutch. For the torque converter with the oil slug, when the oil has deteriorated, the oil slug should be opened and the new oil is used repeatedly. For the torque converter without the oil plug, the method of high pressure air can be used to reverse the cleaning.