A Beijing Mercedes Benz E300L car with a mileage of about 100 thousand km and a model of 211 in 2010. Users reflect: the battery of the vehicle often suffers from insufficient power. It has failed to solve many problems since it has been repaired for many times. Inspection and analysis: maintenance personnel detect the history of vehicle dormancy current, and find fault indication of seat control unit's abnormal sleep current. Measure battery voltage and dormancy current according to maintenance manual. The vehicle is switched to a sleep state with a fault diagnostic instrument. The battery voltage is measured at 12.3 V, normal. The dormancy current is 0.3 mA, normal when the seat back is not folded or adjusted. When the bus of the comfort system control unit LAN is activated, the dormancy current changes to 200 mA, which is also normal. The seat control unit is detected, and the fault code with abnormal initialization of the Holzer sensor is found, so the 2 rotation directions of the adjusting shaft of the servo motor are adjusted. First, the seat adjustment unlocking device is placed in the lock position through the fault diagnosis instrument, and then the servo motor is directed forward 3S first, then the reverse rotation of 3S to complete the initialization of the Holzer sensor. The vehicle was parked for 12 h and it was found that there was still a record of abnormal sleep current in the seat control unit, indicating that the fault still existed. After entering the dormancy state, the dormancy current was observed, and the current suddenly increased to 2A after 3H. Turn off the dynamic seat FDS connector (No. 11 purple), the highly adjusted unlocking switch HES connector (No. 8 colorless), the backrest unlocking switch LES connector (No. 7 Pink), the back / head pillow servo motor L/K connector (No. 6 orange), the tilt adjustment front height V connector (No. 5 Brown), and the longitudinal adjustment L The current of the V connector does not drop, indicating that the problem lies in the control unit. Troubleshooting: replacement of seat control unit, commissioning confirmation troubleshooting.