The flashing red key on the dash of your 2007 Mazda6 is the security indicator light. It indicates that the car's security system is armed. When the car is in use, the light should turn off. When the car is not in use, the light should flash to deter theft.
If the security indicator light is flashing when the car is in use, it may indicate a problem with the security system. You should take your car to a Mazda dealer to have the system checked.
