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

Taking Action
Message Indicated on DisplayMazda 6 Owners Manual: When Trunk Lid Cannot be Opened
If the vehicle battery is dead or there is a malfunction in the electrical system
and the trunk lid cannot be opened, perform the following procedure as an emergency
measure to open it:
1. Open the cover.
2. Move the lever to the left to fold the seatback.
3. Move the lever to the left to o ...
Mazda 6 Owners Manual: Battery recharging
Warning
Keep any flammable away from the battery, otherwise evaporated gas
of the battery fluid may catch fire, and cause serious injury or death.
Caution
When removing the battery, disconnect the negative battery cable
first and install it last to prevent damage to electrical compo ...