A 2009.5 Volkswagen Langevin car with a mileage of about KM million, equipped with a 1. 6L engine and manual transmission. Customer response: when the car radio works, the electric window can not work. Fault diagnosis: after communication with the customer, about one week ago, when the red light was waiting for a red light, the customer heard the noise of the left front door of the vehicle. After closing the ignition switch, the noise disappeared, and the noise appeared again after starting the engine. Then it was found that the radio disappears when the radio works, but the electric car window does not work when the radio works. After the radio is closed, the electric car window returns to normal, but the noise appears, and finally the sound of the left front door speaker is found. Open the ignition switch, hear the driver's side door loudspeaker send out noise, other speakers do not sound, press the driver's side door on the electric car window elevator switch, found that all the electric car windows can not rise and fall, and the customer described the fault phenomenon. What causes the left front speaker to make a strange noise when the radio is not working? Then use the Shanghai Volkswagen special vehicle diagnostic instrument VAS5051 B to read the fault code in the gateway installation list, and find that the 09 - electronic central electronic device has a fault. After the query, a fault code 03020 is found, meaning is the electrical fault (non - incidental) in the 2 circuit of the local data bus. According to the meaning of the fault code and the experience of repairing the vehicle before, it is preliminarily analyzed that the LIN data line of the vehicle may fail. When the LIN data line fails, it will affect the work of the electric window, but it can be seen from the circuit diagram that the LIN data line is not connected with the radio. Why can the electric car window be unable to work when the radio works? The state of the lifter switch is received through the LIN data line. The function of reading and measuring data blocks is used to check the working state of the electric car window lifter switch, and the 012 display group is the state of the lifter switch. Turn off the radio, control the two front lifter switch, the electric window works normally, and read the state of the lifter switch to display manually or manually. This shows that when the radio does not work, the LIN data line can transmit the signal normally, the electric car window can work normally; in the case of the radio working, the two front door elevator switch is manipulated, the electric car window does not work, the state of the elevator switch is not operated. When the radio is working, the elevator switch and the door control unit can not be damaged, which leads to the failure to receive the switch signal of the elevator. It may be the failure of the LIN data line. Because if the LIN data line fails, the signal can not be transmitted, and when the elevator is manipulated, the signal can not be received, so the electric car window does not work. Remove the driver's side door trim board, check the wiring harness not worn, check the circuit diagram to learn that the wiring harness in the lower left front A column has a connection plug, remove the left front A column, pull the plug and find the plug into the water, ask the customer to know that the car has entered the water. When the plug is processed on the radio, the electric window is working normally. Troubleshooting: the plug that handles the influent.