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A mileage of about 130 thousand km, with a model of 220, equipped with 113 engines and 722.6 automatic transmission, 2008 Mercedes Benz S350 sedan. User response: the car feels like driving when driving at constant speed or slow acceleration. Inspection and analysis: the maintenance personnel run the test to make sure that the fault phenomenon reflected by the users is caused by the bad operation of the locking device of the torque converter. According to the specification of the technical bulletin, in this case, the control elements of the torque converter lock clutch should be adaptive to temperature and adaptive operation of 3 locking window periods. Troubleshooting: when the vehicle is fully cooled, start the engine and then replace the D gear. While stepping on the brake pedal, step down the accelerator pedal to maintain this state until the coolant temperature of the engine rises by 20 degrees. Loosen the brake and accelerator pedal, operate at idle speed, let the torque converter cool a little, then repeat the previous step. This cycle is repeated 3 or 4 times until coolant temperature reaches 80 degrees centigrade. Next, when the transmission oil temperature reaches above 60 C, the window period of the converter will start to match. In this process, we need to choose a smooth pavement. First window operation: let the vehicle run at constant speed of 20~40 km/h. The engine speed is controlled at 1200~1500 r/min, the torque of the transmission input shaft is controlled at 20~40 N. M, and the 2 conditions meet the 5S time simultaneously. At this time, the gear shift will shift between the 2~4 gears. Second window operation: let the vehicle travel at a speed of 40 to 80km/h. The engine speed is controlled at 1200~1600 r/min, the torque of the transmission input shaft is controlled at 40.80 N m, and the 2 conditions meet the 5S at the same time. At this time the gear shift will change in the 4~5 gear. Third window period operation: let the vehicle run at constant speed of 40~80 km/h. The engine speed is controlled at 1500~1800 r/min, the torque of the transmission input shaft is controlled at 80~120 N. M, and the 2 conditions meet the 5S time simultaneously. At this time the gear shift will change in the 2~4 gear. At the end of the above operation, at least let the vehicle be in a static state, the idle speed is 10 min, the aim is to ensure that the matching data obtained in the operation is reliably preserved in the transmission control unit.