The mileage is about 106 thousand km, equipped with M272 engine and Mercedes R350 with 722.9 transmission. Due to the long time of parking, the battery is damaged by electricity and the vehicle is unable to start. The owner asked for help, because the operator of the repair shop failed to start the positive and negative operation when the battery was powered up, so the vehicle could not start and had to be dragged to the service station for examination. Fault diagnosis: after the key is inserted into the EIS, the number 15 circuit can be connected. The instrument displays the red warning information and the white information of "ESP currently without this function", and untwisting the EIS to the 50 start up boot machine. The current operation of the gear selection bar is invalid. The DAS diagnostic instrument is connected to the vehicle for rapid testing, and the key information is displayed. From the quick test, it can be seen that the current vehicle has multiple control modules and the DAS diagnostic instrument can not communicate, the cause of the analysis of the fault is the cause of the power supply, should be the main power supply circuit power failure. Based on the principle of easy and difficult first, the main power supply of the right front fuse box of the engine room is measured first, and no voltage is found here. After checking the relevant circuit diagrams, it is learned that the components that are responsible for the power supply to the right front fuse relay box F58 of the engine room are the front fuse box F32 eighth fuse. The front fuse box F32 is located in front of the air inlet of the engine room on the right. It is found that the fuse of F8 has been fused and the same type fuse has been tested and troubleshooting. Fault summary: This is a typical vehicle power supply system fault, to understand the fault model of the circuit diagram to eliminate such faults can be twice the result of twice the result.