If your vehicle rapidly closes in on the vehicle ahead because the vehicle applies the brakes suddenly while you are traveling in headway control, the warning sound activates and the brake warning is indicated in the display. Always verify the safety of the surrounding area and depress the brake pedal while keeping a safer distance from the vehicle ahead.
Additionally, always keep a safer distance from the vehicles behind you.

Mazda Radar Cruise Control (MRCC) Display Indication
Setting the SystemMazda 6 Owners Manual: Front door speaker inspection
1. Inspect for resistance between the front door speaker terminals using an
ohmmeter.
If not as specified, replace the front door speaker.
2. To verify that the front door speaker outputs sound, apply voltage to the
front door speaker and release using a 1.5-V battery.
If not outp ...
Mazda 6 Owners Manual: Registering Your Vehicle in A Foreign Country (Except United States and Canada)
Registering your vehicle in a foreign country may be problematic depending on
whether it meets the specific emission and safety standards of the country in which
the vehicle will be driven. Consequently, your vehicle may require modifications
at personal expense in order to meet the regulation ...