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 wheel alignment
Specification (Unloaded)*1
Normal
Elevated*3
*1 : Engine coolant and engine oil are at specified level. Spare tire, jack
and tools are in designated position.
*2 : Difference between left and right must not exceed 1°30'.
*3 : Distance between wheel center and fender brim is 402 mm {15.8 ...
Mazda 6 Owners Manual: Dual proportioning valve replacement (without abs)
1. Remove in the order indicated in the table.
2. Install in the reverse order of removal.
Dual Proportioning Valve Installation Note
Install the dual proportioning valve so that the R mark faces the left side
of the vehicle.
...