If the theft-deterrent system detects an inappropriate entry into the vehicle, which could result in the vehicle or its contents being stolen, the alarm alerts the surrounding area of an abnormality by sounding the horn and flashing the hazard warning lights.
The system will not function unless it's properly armed. So when you leave the vehicle, follow the arming procedure correctly.
Mazda 6 Owners Manual: Front Passenger Occupant Classification Sensor
Your vehicle is equipped with a front passenger occupant classification sensor
as a part of the supplemental restraint system. This sensor is equipped in the front
passenger's seat cushion. This sensor measures the electrostatic capacity of the
front passenger's seat. The SAS unit is designed ...
Mazda 6 Owners Manual: Smart Brake Support (SBS) (Some models)
The Smart Brake Support (SBS) system alerts the driver of a possible collision
using a display and warning sound if the radar sensor (front) and the Forward Sensing
Camera (FSC) determine that there is the possibility of a collision with a vehicle
ahead while the vehicle is being driven at abo ...