The mileage is about 43 thousand km, and the engine is SQR6471 B 147 2012 Chery. The window glass lifting master switch on the driver's side door can only control the drop of the window glass of the left front car, and can not control the other window glass lifting, while the window glass lifting switch on the right front, left rear and right rear door can control the window and glass of the corresponding car. Fault diagnosis: it is known from the electric window control circuit of the car that the body control module (BCM) receives the control signal of the window glass lifting switch (iron lap signal), and then controls the work of the corresponding glass elevator motor. Taking into account that BCM will be in a dead condition during its use, the battery will be disconnected for a few minutes before it can be reloaded. A careful analysis of the electric window control circuit of the car shows that the window glass lifting master switch and the window glass lifting switch on other doors share the control signal lines, such as the BCM terminal A11 not only receives the right front window glass drop signal from the window glass main control switch, but also receives the window glass from the right front door. Drop signal for front right window glass of lift switch. Since the window glass lifting switch on the right front, left back and right rear doors can normally control the window and lift of the window, it shows that the fault is caused by the window glass lifting master switch which can not transfer the corresponding window glass lifting signal to BCM. The possible fault is due to the main control switch loss of the window glass lifting and lifting. Bad; a related line fault. Check the left front door wiring harness. It is found that the link between the left front door wiring harness and the body wiring harness is seriously corroded and some wires have been broken. Further examination revealed that the seal sleeve of the left front door wiring harness and the wiring harness of the body was broken, causing the rain to enter. Troubleshooting: replace the wiring harness and the corresponding sealing sheath, and clean up the wiring harness of the car body after the trial run, troubleshooting.