What it means
The BMS detects that battery pack subsection I is operating above the safe temperature threshold. Cell-level cooling or pack thermal management is compromised on this section.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The battery management system (BMS) monitors temperature readings for battery pack subsection I and manages cooling to keep its cells within a safe range. This code sets when the reported temperature for subsection I exceeds the BMS threshold.
Common causes
Most likely first.
- Coolant flow to this section reduced
- Cell imbalance causes local heating
- Ground point with elevated resistance
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Record freeze-frame data and compare live temperatures for subsection I with the other pack sections to confirm whether the reading is persistently high or an outlier.
- Check the battery cooling system for low coolant, leaks, blocked passages, or other signs that flow to subsection I may be restricted.
- Inspect accessible connectors, wiring, and the ground point serving the subsection I temperature and cooling circuits for looseness, corrosion, damage, or heat marks.
- Use scan data to compare cell voltages and temperatures in subsection I with neighbouring sections for imbalance or a localized hot spot.
- Test the subsection I temperature-sensor circuit and ground for continuity, resistance, and voltage drop against the manufacturer's specification before condemning pack components.
Common fixes
- Restore coolant level and correct any leak or restriction in the battery cooling path.
- Clean and secure a corroded or loose ground connection serving subsection I.
- Repair damaged wiring or terminals in the subsection I sensor or cooling circuit.
- Correct a confirmed cell imbalance or replace a failed pack component identified by testing.
Can I keep driving?
Avoid charging or demanding high power while the warning is active; the vehicle may reduce output or enter limp mode. Stop safely if the warning escalates, power drops sharply, or the pack shows signs of overheating, since continued use can worsen battery damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.