A TOYOTA Camry. Users reflect, after parking brake, brake pedal automatically sink, vehicle movement, brake failure, at the same time the instrument multi-functional display display "please check brake system failure." Step on the brake pedal, the pedal height is a little lower. After receiving the car: use IT-II to check, there is trouble code C1441 brake booster failure. Because brake system has trouble code prompt, check brake booster according to fault code, normal. Check each brake wheel cylinder and pipeline no oil leakage marks, connect the oil pressure gauge on the exhaust hole of the wheel cylinder. After the oil pressure meter is exhaust, the brake pedal reads the pressure of the system. Compared with the same type, the pressure is normal. When the pressure testing is done, the pressure is reduced a little bit by bit, indicating that the system is in the pressure relief failure. When the vehicle is not starting, the ABS pump plug is removed and the pressure protection experiment is continued. The pressure drops obviously. This can exclude the failure of the ABS pump. Finally, it is determined that the fault point is the pressure relief of the main brake cylinder. Replace the main cylinder, exhaust, and troubleshooting. Maintenance summary: new accessories do not mean no problem. According to the basic principle of the system, the failure point can be found by using simple equipment.