The Audi A6L (C7) car with a mileage of about 3500 km. Users reflect that the engine will suddenly flameout in the course of the driving, and the engine can start the machine immediately after the fire is extinguished, and sometimes it takes a few hours to start the machine. Fault diagnosis: connect VAS6150B to detect the vehicle, and there is no fault code stored in the engine control unit. After understanding, there was no rule of failure, and there were 3 times in the last 2 months. Check the power supply and iron lap of the engine control unit, normal; measure the pressure of the fuel system, and also in the normal range; exchange fuel pump control unit (J17), bus end 15 power relay (J329), main power supply relay (J271), engine component power relay (J757) test with the running normal same type vehicle The car, by fourth days through multiple road test in the process of no failure, and back to the factory after a period of time, the engine can not start the failure (the engine starting 3 times did not start successfully, the fourth start and resumed normal). Immediately connected to the VAS6150B, the fault code in the engine control unit is P0652 00 (165), which means the sensor standard and the voltage B is too low. According to the VAS6150B navigation function hint, it is required to test the output voltage or line of the connector terminals T60/35, T60/58 and T94/63 of the engine control unit (J623). Access to information shows that the power supply components of these terminals are listed in Table 1. The output voltage of the J623 connector terminals T60/35, T60/58 and T94/63 can be measured when the engine can start normal starting, all 5V, normal, and when the engine can not start, the output voltage of J623 connector terminal T60/35 and T60/58 is 5V, normal; and terminal T94/63 output voltage is only 4V, abnormal. The wiring harness of the engine is measured, and the wire connected to the terminal T94/63 has no short circuit, circuit breakage and bad contact. Therefore, the fault point is confirmed to be a problem of the J623 body, so J623 is replaced, but after 1 months, the car is re entered and repaired, reflecting the above failure. When the vehicle enters the factory, the engine starts normally, connected to VAS6150B for testing, and no fault code storage. During the third day trial run, the fault occurred, so the field was tested. The output voltage of the connector terminal T94/63 of J623 is still only 4V. Then the component wire connector that is powered by the terminal is checked one by one, and when the G513 wire connector is broken, the output voltage of the terminal T94/63 becomes 5V, which determines that the fault is on the G513. Troubleshooting: the replacement of G513, after a long time test, failure has not been reproduced, the car after the factory many times to call back, the drive has been normal, troubleshooting.