A Chevrolet Cruz with a mileage of about 25 thousand km. The owner reflected that the rear window switch of the car could not control the lifting of the glass. After receiving the car, the window motor control circuit is applied to the right rear window motor control circuit by the right rear window switch, and the negative pole is applied to the other car window motor control circuit. The voltage leads to the window opening; when the switch is up, the negative positive and negative voltage of the reverse direction is provided to the motor window motor so that the window is closed. When the switch is switched, a serial data information is sent to the body control module to request the window motor instruction BCM to send serial data to the corresponding window switch, which then moves the instruction window in the required direction. According to the maintenance manual circuit test, disconnect the S79RR right rear window switch plug, use the multimeter to test whether the 5 terminal and ground resistance are less than 2 Omega, the test result is 0.5 Omega, indicating that the grounding is normal. Place the ignition switch in the ON position. Use the test lamp to test whether the test lamp between the S79RR plug 8 terminal B+ and the ground is lit. With two 3A short wiring, one connecting S79RR Plugs 7 and 5 terminals, another short connection connecting 8 and 6 terminals, the test results are rising; on the other hand, one line connects S79RR Plugs 6 and 5 terminals, another short connection is connected to the 8# and 7 terminal sub windows, and the test results are Down, indicating that both the line and the motor are normal. The ignition switch is placed in the OFF position, disconnects the negative pole of the battery, disconnects the X2 line connector of the body module, and uses the multimeter to test whether the resistance between the X2 LIN line 21 terminal and the S79RR plug 1#LIN line terminal is less than 2 Omega, the test result is larger than the specified range, indicating that the resistance of the serial data line is too large. The inspection line found that when the fault point ----B column was welded, the wire harness of the X800 connector was melted by high temperature, so the LIN line was glued together with the multiple lines and could not communicate. The right rear window could be lifted and lifted after the damaged wire harness was treated and repaired.