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: Crash zone sensor removal/installation
Warning
Handling the crash zone sensor improperly can accidentally deploy the air bag
module and pre-tensioner seat belt, which may seriously injure you. Read AIR BAG
SYSTEM SERVICE WARNINGS before handling the crash zone sensor. (See SERVICE
WARNINGS.)
1. Turn the ignition switch to LO ...
Mazda 6 Owners Manual: Front seat disassembly/assembly
Warning
Handling the front seat (side air bag) improperly can accidentally
deploy the side air bag, which may seriously injure you. Read AIR BAG SYSTEM
SERVICE WARNINGS before handling the front seat. (See SERVICE WARNINGS.)
1. Disconnect the negative battery cable and wait for more tha ...