2012 Toyota Prius Owners Manual - Page 810

5-2. Steps to take in an emergency Warning message Details (Flashes) Indicates a malfunction in the radar cruise control system. A buzzer also sounds. Press the "ON-OFF" button once to deactivate the system, and then press the button again to reactivate the system. (If equipped) (Flashes) Indicates a malfunction in the LKA. A buzzer also sounds. (If equipped) 510