An omman diesel fuel injection tank car, the driver reflected: the car started the car, press the fault diagnosis switch, the fault code is "71", that is, the PCV1 valve output short circuit or circuit breakage, so only the PCV2 valve work, rail pressure obviously can not reach the normal state, vehicle power decline is not difficult to understand. Using voltmeter to measure two lines of PCV1 valve, all two lines are power supply voltage. It seems that the power supply is normal. Then disconnect the key switch to extinguish, pull out the PCV1 valve socket, measure the PCV1 valve value of normal, about 3 Omega, and deduce the fault between the PCV1 valve control line to the ECU / 152 and 153 line between the feet. Open the front hatch of the cab, pull down the upper and lower connection ports of the cab wiring harness to the engine, and measure the unconnected lines of the port to the PCV1 valve socket. Check the wiring harness along the related harness, and when the harness of the lower part of the cockpit is unlocked, the bellows of the harness have been worn and a light green wire is squashed. Although the glue is connected, the copper wire inside it has been broken. The wire harness fixed card was a metal product. In the long term bump of the vehicle, the wire harness corrugated pipe and the wire rubber were worn, and the long water vapor infiltration was added, which caused the line to be broken and caused the breakdowns. After the bandage is processed, the fault is excluded.