Function Description

The BSW system can help alert the driver of other vehicles in adjacent lanes when changing lanes.
The BSW system uses side radars installed near the rear bumper to detect vehicles in an adjacent lane.
The side radars can detect vehicles on either side of vehicle within the detection zone shown as illustrated.
This detection zone starts from the outside mirror of vehicle and extends approximately 10 ft. (3.0 m) behind the rear bumper, and approximately 10 ft. (3.0 m) sideways.
The BSW system operates above approximately 20 MPH (32 km/h).
If the side radar detects vehicles in the detection zone, the Blind Spot Warning indicator illuminates.

Fig 1: Overview Of BSW System (Indicator ON)
Courtesy of NISSAN NORTH AMERICA, INC.
If the driver then activates the turn signal, a buzzer will sound twice and the Blind Spot Warning indicator will blink.
NOTE:
A buzzer sounds if the side radar has detected a vehicle when the driver activates the turn signal. If a vehicle comes into the detection zone after the driver activates the turn signal, then only the Blind Spot Warning indicator blinks and no buzzer sounds.

Fig 2: Overview Of BSW System (Indicator Blink With Buzzer Sound)
Courtesy of NISSAN NORTH AMERICA, INC.