Take the appropriate action and verify that the warning light turns off.

Taking Action
Message Indicated on DisplayMazda 6 Owners Manual: Operation
System triggering conditions
The horn sounds intermittently and the hazard warning lights flash for about
30 seconds when the system is triggered by any one of the following:
Unlocking a door with the key, door lock switch, or an inside door-lock
knob.
Forcing open a door, the hood or th ...
Mazda 6 Owners Manual: Thermostat
THERMOSTAT REMOVAL/INSTALLATION
1. Remove the plug hole plate.
2. Disconnect the negative battery cable.
3. Drain the engine coolant. (See COOLING SYSTEM SERVICE WARNINGS.)
4. Remove the drive belt. (See DRIVE BELT REPLACEMENT.)
5. Remove the washer tank.
6. Remove the P/S oil pump.
Note
...