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: Rear door removal/installation
Warning
Handling the side air bag sensor improperly can accidentally
deploy the side air bag module, which may seriously injure you. Read AIR BAG
SYSTEM SERVICE WARNINGS before working around the B-pillar areas. (See
SERVICE WARNINGS.)
Note
The side air bag sensor is located in t ...
Mazda 6 Owners Manual: Dtc clearing procedure
1. Start the on-board diagnostic test mode.
2. First press the POWER button, then simultaneously press AUDIO CONT button
for 2 seconds or more.
Caution
Before clearing the DTCs, be sure to enter all of them displayed
in the on-board diagnostic test mode in the Audio Repair Order Form. ...