A car with a mileage of about 40 thousand km and a F18 520Li powered BMW 520Li car equipped with N52 engines. User response: the left rear window lifter is abnormal. Inspection and analysis: the maintenance personnel test the car. In the moment of operating the glass lifter button, the left rear glass is slightly fretting. When the button is kept operating, the glass will not respond. Detect the body control unit and find the indication of the fault of the left rear glass lifter Holzer sensor.