CUSTOMER CONCERN The brake pedal drops to the floor and remains low after repeated bleeding attempts, with DTC C1246 stored. CAUSE Blocking the master-cylinder outlets and the hydraulic noise at the master cylinder isolated an internal brake master-cylinder failure rather than residual air alone. CORRECTION Remove and replace the failed brake master cylinder, perform the complete Prius brake air-bleed procedure, reset ABS memory and required initialization, clear DTC C1246, a