A Audi A6L car with a distance of about 130 thousand km. Customer response: after the vehicle starts, the engine idle speed is about 1000r/min, and the speed does not decrease. Fault diagnosis: first test car, test car did not find fault phenomenon, vehicle after maintenance, start the engine, found idle speed around 1000r/min, speed does not reduce, instrument generator alarm light light. The cause of the high idle speed of the A6L engine is usually due to the damage of the crankcase ventilation valve, which causes a large amount of gas to enter the cylinder in the crankcase; the active carbon tank solenoid valve will also lead to high idle speed, and the throttle card can also cause high idle speed in a certain position. The fault free storage in the engine control unit is detected by VAS5052, and the fault code in the gateway J533 shows that the battery monitoring and control unit J367 has a fault, and the fault code can be deleted. Considering that the generator alarm lamp is lit, the reason for the high idle speed may be related to it. Because the A61 - model has the power management control unit J644, J644 has many functions, one of which is to improve the engine idle speed, to optimize the power supply and battery charging voltage of the vehicle. The 2009 Audi A6L cancelled the J644, and the energy management of the battery was operated by gateway J533. The J533 is connected to the battery monitoring and control unit J367 through a LIN conductor. J367 is used to detect three parameters of battery charging and discharging current, battery voltage and battery temperature. Now, because of the failure of the J367, the three parameters of its monitoring are inaccurate, and the error information is transmitted to the J533. J533 is mistaken for the insufficient charging voltage of the battery, sending out information to the engine control unit, and requiring the engine to lift the idle speed to improve the charging voltage. After replacing the battery monitoring and control unit J367, troubleshooting.