2010 Toyota Sequoia Owners Manual - Page 239

2-4. Using other driving systems ● If an obstacle has been detected within 15.7 in. (400 mm) of the front or 33.5 in. (850 mm) in rear of the vehicle (a continuous buzzer is sounding), and a new obstacle is detected at the same way at the other end of the vehicle, the buzzer will sound 3 times then one continuous buzzer. Sensors that operate and detection range The following diagrams show the sensor detection range. Note that sensors may not be able to detect obstacles that are extremely close to the vehicle.