What this code means

The 12V AGM or EFB battery state of health has degraded below the minimum threshold required for reliable start-stop operation.

Symptoms

• Start-stop permanently disabled
• Battery management warning
• 12V battery struggles in cold weather
• Electrical systems may exhibit issues
• Start-stop light always off
• Higher fuel consumption without start-stop

Common causes

• Battery age exceeding service life
• Excessive parasitic draw degrading battery
• Battery not properly maintained
• Wrong battery type installed (non-AGM/EFB)
• Frequent short trips not fully recharging battery

Diagnostic steps

1. Read battery state of health via IBS/BMS
2. Load test 12V battery
3. Check battery type matches vehicle specification
4. Test charging system output
5. Measure parasitic draw

Repair notes

Replace 12V battery with correct AGM or EFB specification. Register new battery with vehicle BMS. Standard flooded batteries are not suitable for start-stop vehicles.

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