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: Dtc c1955, c1956
Caution
When attaching the tester lead to the DSC HU/CM connector the SST
(49 G066 004) must be used.
Diagnostic procedure
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Mazda 6 Owners Manual: Radiator cap
Warning
Never remove the radiator cap while the engine is running, or when
the engine and radiator are hot. Scalding coolant and steam may shoot out
and cause serious injury. It may also damage the engine and cooling system.
Turn off the engine and wait until it is cool. Even then, be ve ...