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

Taking Action
Message Indicated on DisplayMazda 6 Owners Manual: Seat belt inspection
Belt
1. Confirm that the seat belt is installed correctly.
2. Inspect the seat belt for damage and deformation of metal parts.
If any damage is found, replace as necessary.
ELR
1. Verify that the belt can be pulled out smoothly, and that it moves
smoothly when wound.
If not as specif ...
Mazda 6 Owners Manual: Locking, Unlocking the Doors
NOTE
The system may not operate if you are too close to the windows or door
handles.
If the key is left in the following areas and you leave the vehicle,
the doors may be locked depending on the radio wave conditions even if the key
is left in the vehicle.
Around the dashboard
...