What it means
The BMS detects at least one cell with voltage below the safe lower limit. Risk of cell damage from deep discharge.
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 monitors individual cell or cell-group voltages in the hybrid or EV pack. This code sets when at least one monitored cell falls below the system's lower voltage limit, which can trigger power or charging restrictions to protect the pack.
Common causes
Most likely first.
- Cell heavily aged - capacity reduced
- Deep discharge event
- Pack cell imbalance approaching service threshold
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
- Save freeze-frame data and BMS codes, then identify the lowest reported cell voltage and the conditions when it occurred.
- Compare the low cell's voltage with the other cell readings and review its change during vehicle operation or charging using approved scan data.
- Inspect accessible low-voltage BMS sensor connectors and wiring for damage or poor connections, following the manufacturer's high-voltage safety procedures.
- Check whether the low reading persists after the pack has been safely rested or charged as directed by the manufacturer.
- If the reading is confirmed and wiring is sound, have the affected cell group and pack balance evaluated with the manufacturer's approved battery test.
Common fixes
- Repair a confirmed BMS sensing wire or connector fault causing a false low reading.
- Correct an identified deep-discharge or charging condition using the manufacturer's prescribed recovery process.
- Rebalance or service the pack if the manufacturer allows it and testing shows imbalance.
- Replace the affected cell module or pack component if testing confirms reduced capacity or cell damage.
Can I keep driving?
Avoid continued driving or repeated charging if the vehicle reports a low battery-cell warning, reduced power, or limp mode; deep discharge can permanently damage a cell. Arrange prompt battery-system diagnosis and stop if power becomes unpredictable.
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.