2010 Toyota Yaris Owners Manual - Page 191

2-4. Using other driving systems When the VSC/TRAC are operating If the vehicle is in danger of slipping or the front wheels spin, the indicator flashes to indicate that VSC/TRAC have been engaged. A buzzer (intermittent) sounds to indicate that VSC is operating. 2 When driving To disable TRAC and/or VSC (vehicles with VSC OFF switch) If the vehicle gets stuck in fresh snow or mud, TRAC or VSC may reduce power from the engine to the wheels. You may need to turn the system off to enable you to rock the vehicle in order to free it.