The mileage is about 80 thousand km, and the model is E70, the BMW X5 sport utility vehicle equipped with N55 engine and 8 transmission automatic transmission in 2012. User response: when the vehicle runs at high speed, the water temperature often reports to the police, and the fuse of the fuel pump has fuses many times. After the above situation, the air conditioner is not refrigerating, and the function of the rear window anti clamping is lost. Inspection and analysis: the maintenance personnel failed to find the problem during the trial run, so they decided to start with the air conditioner. Check the air conditioning control unit and find the indication of the fault of the pressure sensor of the refrigeration system. Read the high voltage data for 255 kPa. If the data is the actual value, the air conditioning will definitely not refrigerate. Measured by instrument, the pressure value is normal, indicating that there is something wrong with the pressure measurement system of the air conditioning control unit. But after changing the sensor, the data did not change. Looking at the circuit diagram, it is found that the pressure sensor is connected to the smart junction box. Further observation shows that the rear window lifter is also connected to the smart junction box. Is the junction box broken? It seems unlikely. Careful observation shows that 2 oil level sensors in the fuel tank are connected to the smart junction box. This discovery reveals the subtle link between fuse fuses and fault points. If the oil level indication is incorrect, when the oil level in the fuel tank is too low, the fuel pump is likely to overload and lead to fuse fuses. At this point, the abnormal reason of the air pressure sensor and fuel tank oil level sensor is connected with the intelligent junction box. The problem is likely to be here. Troubleshooting: after changing the smart terminal box, visit the users several times and confirm that the trouble is completely eliminated.