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The BMW F02 730Li car with a N52 engine model. During the normal driving process, the generator does not generate electricity, and can not detect the fault of oil level. Troubleshooting: after receiving the car, it is found that the car can not start again after the car is parking, lap the battery, start the car and open back to the factory, and find that the car can not detect the oil level. The diagnostic apparatus was attached and several fault codes were found. After querying, there is only BSD bus communication failure. According to the circuit diagram, there are generator (G6524), oil state sensor (B62540) and electric coolant pump (M6035) on the BSD bus. Find the bus (36, 37, 42 ports) at the computer plug of the engine, use multimeter to measure, no voltage. Normally, when the ignition switch is switched on, the voltage will be about 8V. Remove the components on the bus, respectively (but must ensure that there is always one part connected to the bus), but no matter which one is pulled off, there is no voltage output on the bus. It is possible to judge the possibility of a computer damage. The bus is short circuited by the multimeter. Open the front door of the engine, and find that the elements associated with BSD are on the back of the computer board. The back shell is hard to open. Only the back of the back and the BSD associated element are cut open (find 1 waste computers, disassemble, determine the position related to the BSD element, find the exact position, and then cut the computer that needs maintenance with the grinding wheel). Measuring along the needle, it is found that the BSD bus has entered 1 models of 27u transistors, which have been inserted into 8 pin chips of 1 IJA 1020 through triode. By querying data, IJA 1020 is found to be a communication chip. Measurement of triode, breakdown. In order to achieve a high coefficient of success, we decided to replace the communication chip with the transistor, so we contacted the electronic component supplier to deliver the goods. After receiving the components, it will be installed and tested. There will be voltage on the bus. When all the components on the bus are plugged in, there is no voltage again, indicating which part of the bus is defective. The components are removed one by one, and the voltage is normal when the generator is removed. Then the generator was replaced, and the starting vehicle was normal. The oil level can also be displayed on the central display screen, and the generator voltage is normal. The fault code is cleared, and the BSD bus communication failure code is not reproduced. Maintenance summary: through the case of maintenance analysis, we can see that, for the maintenance of high-end models, the key is to identify the source of the problem, can not replace the assembly components blindly. It is particularly important to diagnose the electrical faults of high-end models, and it is also very important for the precise inspection of electronic components. Because the electronic control system is more and more precise in the calculation of information and the requirement for control is higher and higher, traditional maintenance is bound to be a history. Changing the traditional maintenance concept and setting up the correct scientific thinking concept are the prerequisites for the new generation of auto repair people.