The 2012 Land Rover Aurora 2.0T cars with mileage of about 10 thousand km. User response: when the cold car starts, the rear part of the car is abnormal, and sometimes it will appear in the running. Fault diagnosis: the customer reflects the rumbling of the rear part of the vehicle, and the failure of the vehicle entering the station to check the test run. Further examination of the abnormal sound location revealed that the abnormal sound came from the inside of the fuel tank, similar to the vibration of the oil pump. Lift the vehicle, remove the fuel tank for inspection, no special phenomenon, replace the new fuel pump and fuel tank trial run, the failure is still. Check the fuel vapor emission system is normal, remove all the fuel vapor discharge pipeline, the failure is still. The failure phenomena are analyzed: (1) confirm that the abnormal sound comes from the fuel pump inside the fuel tank. (2) inquire the relevant data to understand that the car has no fuel oil return pipeline, the low pressure fuel pump supply oil depends on the voltage regulation of the low pressure fuel delivery control unit to change the pressure in the low pressure fuel line. (3) does the fuel pump overload produce abnormal noise? (4) the reasons of overloading operation of Shantou pump are: the error of the low pressure fuel pressure sensor signal, the failure of the low pressure fuel delivery control unit and the failure of the power supply line of the low pressure fuel pump. The examination is carried out according to the above analysis. The fuel pump is simulated, the fuel pump plug is pulled out, the fuel pump motor is powered 12.5V, Shantou pump running, the "goo" abnormal sound appears, which is determined to be the abnormal sound of the high speed operation of the fuel pump. Replace the new low pressure fuel pressure sensor and the low pressure fuel pump delivery control unit. Check according to the circuit diagram, start the vehicle, measure the oil pump transmission control unit, supply the C4E220E-4 foot voltage to 14.7V, normal. The voltage at C4E220E-3 and C4E220E-6 is 14.7V, and the voltage is too high (the normal voltage is about 5.7V). The voltage of measurement C4E220E-6 is 14.7V, normal. The voltage of the measurement C4E220E-3 is 0V, which is not normal. Break off battery negative pole, pull out C4E220E and C4E515 plug, measure C4E220E-6 to C4E515-4 good conduction. The measurement of C4E220E-3 to C4E515-3 is good. The short-circuit grounding phenomenon was not detected by measuring the C4E220E-6 to the ground. The measurement of C4E220E-3 on the ground reveals that there is a short-circuit iron connection phenomenon. Along the line inspection, there is a short-circuit phenomenon in the C4E515-3 line of the C4E515 plug rear line and the C4E515-5 line (the tie line) of the parcel C4E515-3 and the C4E515-4 line. According to the fault repair line, the test car fault is excluded.