2009 Toyota Sienna Owners Manual - Page 239

2-4. Using other driving systems n Back sensor operation and distance to an obstacle The system operates when the vehicle approaches within following distance to an obstacle. The indicator flashes and the buzzer sounds when the system is operating. 2 When driving ft. (cm) Distance to an obstacle Approximately 5.9 - 3.0 (180 - 90) Approximately 3.0 - 1.8 (90 - 55) Approximately 1.8 or less (55 or less) Indicator and buzzer Intermittent Fast intermittent Continuously 211