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: No.4 air intake mode does not change
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while performing the inspection to discover
whether poor contact points are the cause of any intermittent malfunctions.
If there is a problem, check to make sure connectors, terminal ...
Mazda 6 Owners Manual: Dsc system inspection
Preparation
1. Verify that the battery is fully charged.
2. With ignition switch on, verify that the ABS warning light goes out after
2.4 seconds.
3. Turn the ignition switch off.
4. On level ground, jack up the vehicle and support it evenly on safety
stands.
5. Shift the transaxle to N posi ...