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: Dtc table
Note
Perform the following if the security light stays on:
- If gasoline engine stalls, go to symptom troubleshooting NO.11
ENGINE STALLS/QUITS, ENGINE RUNS ROUGH, MISSES, BUCK/JERK,
HESITATION/STUMBLE, SURGES in. (See NO.11 ENGINE STALLS/QUITS, ENGINE RUNS
ROUGH, MISSES, BUCK/J ...
Mazda 6 Owners Manual: Anti-theft system
Alarm Conditions
If the anti-theft system protection has been activated, any one of the
following conditions will trigger the system:
- Disconnected battery cable
- Discharged battery
- Disconnected audio unit connectors
If the system is triggered, the audio unit will then be ...