A low level of electrolyte fluid will cause the battery to discharge quickly.

Inspect the electrolyte level at least once a week. If it is low, remove the caps and add enough distilled water to bring the level between the upper and lower level (illustration).
Do not overfill.
Examine the specific gravity of the electrolyte with a hydrometer, especially during cold weather. If it is low, recharge the battery.
Battery Maintenance
Battery RechargingMazda 6 Owners Manual: Transaxle oil inspection
1. Park the vehicle on level ground.
2. Remove the oil level plug and washer.
3. Verify that the oil is near the brim of the plug port.
If the oil level is lower than the low level, add the specified amount
and type of oil through the oil level plug hole.
Specified oil grade
API Ser ...
Mazda 6 Owners Manual: Dtc c1145, c1155, c1165, c1175
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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