An Oman tanker equipped with a diesel electric common rail engine is used to turn off the gears when reversing the gears. Check on the car, ECU main fuse to burn, the replacement of the new same specification fuse, starting the car all normal, again when the reverse gear, you hear a "snap" sound, the car extinguished, the newly replaced fuse and burn. Referring to the circuit diagram, ECU main fuse not only provides power to ECU, but also supplies power to many functional switches, such as empty switch, reversing switch, clutch switch and so on. Since it is a reversing gear to burn the fuse and extinguish, then the reversing switch or the reversing switch to the ECU line has a tie - in condition. In line with the principle of "first easy and difficult", first check the transmission line harness and reversing switch, do not find the fault point, check the chassis harness and the cab wiring harness one by one, and find no problems. Finally, the guard plate in the middle position of the cab is removed. ECU is installed in this place, and the ECU wiring harness is not protected by the bellows. Just wrap two loops with plastic tape, and do not have a clip fixed protection. One of the green and white lines is pierce by the iron burr of the lower part of the cab and the iron is laid. Then clean up the iron burr, wrap up and fix the wiring harness, and test everything is normal. In the future maintenance work, I have found that the ECU main fuse has been broken because of a large number of switching lines (such as empty switch, reversing switch, clutch switch and other lines), causing the vehicle to extinguish. According to the high failure rate of many switching lines, the author suggests that the fuse protection should be set up separately between the main power supply of ECU and many switching lines, in order to improve the safety and economy of vehicle driving.