P3201critical severityPowertrain
Hybrid/EV Battery Cell Voltage Imbalance
on 2010 Toyota Highlander 3.3L V6 Hybrid · AWD
What this code means
One or more cells in the HV battery pack have significantly different voltage levels from the rest. Cell imbalance reduces pack capacity and can indicate cell failure.
Symptoms
- Hybrid/EV warning light
- Reduced electric range
- Battery SOC drops rapidly
- Inconsistent regenerative braking
- Power output limited
- Uneven charging behavior
Common causes
- Individual cell degradation
- Cell internal resistance increase
- Temperature variation across pack
- BMS balancing circuit failure
- Manufacturing defect in cell
Diagnostic steps
- Read individual cell voltages via scan tool
- Identify weakest cell or module
- Check cell temperatures across pack
- Test cell internal resistance
- Review BMS balancing history
Repair notes
Replace failed battery module(s). In some vehicles, individual modules can be replaced. Full pack replacement if multiple modules affected.
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