What this code means

The auxiliary systems that maintain cabin comfort during engine-off periods (electric A/C compressor or thermal storage) are not functioning.

Symptoms

• Start-stop deactivates quickly in hot/cold weather
• Cabin temperature drifts rapidly during stops
• A/C blows warm air at stops
• Start-stop durations very short
• Reduced fuel savings from start-stop

Common causes

• Electric A/C compressor failure
• Thermal storage evaporator issue
• Auxiliary coolant pump fault
• Electric heater element failure
• Control module communication error

Diagnostic steps

1. Check auxiliary A/C compressor operation during engine stop
2. Monitor cabin temperature drift rate
3. Test auxiliary coolant pump
4. Check electric heater circuit
5. Monitor start-stop inhibit reasons

Repair notes

Replace auxiliary A/C compressor or electric heater. Repair auxiliary coolant pump if cabin heating affected.

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