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: Manifold absolute pressure (map) sensor inspection
Note
Perform the following inspection only when directed.
The following vacuum values are indicated by relative pressure
from the MAP sensor.
1. Connect the SSTs (WDS or equivalent) to the DLC-2.
2. Turn the ignition switch to ON (Engine OFF).
3. Select MAP PID on the SSTs (WDS or equi ...
Mazda 6 Owners Manual: No.4 air intake mode does not change
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while performing the inspection to discover
whether poor contact points are the cause of any intermittent malfunctions.
If there is a problem, check to make sure connectors, terminal ...