The mileage is about 29 thousand km, which is equipped with the 2.0T T5 engine and the DCT double clutch transmission in 2011 to import the Volvo S60 car. User response: the vehicle has abnormal sound similar to sharp whistling at idle speed. Inspection and analysis: the maintenance personnel first confirm the vehicle failure after the car, and there is a whistling sound described by the user when the vehicle is idle. First, it is doubted that the noise should come from the intake pipe. So the maintenance personnel disassembled the intake hoses to check whether there was any jam or leak position, but the inspection results were all normal. After the intake hose is reloaded and tested, it is found that the abnormal sound still exists, listening carefully to the sound source emitted by the abnormal sound, and it is found that the abnormal sound is generated near the turbocharger. Check the vacuum tubes and vacuum hoses of turbochargers and find no blockage or leak. The noise of the vehicle was caused by a very serious leakage, so the maintenance staff tried to block the intake of the vacuum pipe of the turbocharger. When the vacuum hose of the turbocharger was blocked, the screech of the engine at idle speed disappeared, indicating that the failure was closely connected with the vacuum hose. The maintenance personnel seized the clue and continued to check the other side of the vacuum hose, and found that the other end of the vacuum hose was connected with the electromagnetic bypass valve of the turbocharger. Check the turbocharger electromagnetic bypass valve and its related lines. No abnormalities were found. A careful inspection of the electromagnetic bypass valve of the turbocharger is carried out to detect the rupture of the vacuum diaphragm inside the electromagnetic bypass valve, which is the direct cause of the engine's whistling sound at idle speed. Troubleshooting: since the damaged electromagnetic bypass valve does not have separate fittings, the turbocharger of the defective vehicle is replaced and tested, and the trouble is eliminated.