What it means
The high-voltage system voltage is below the expected window. HV battery output drops, isolation event, or loaded too heavily.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The high-voltage battery supplies the vehicle's electric drive and hybrid functions, and the battery management system monitors pack voltage during operation. This code sets when the measured high-voltage system voltage falls below its expected range, which can lead the vehicle to limit power or electric operation.
Common causes
Most likely first.
- HV battery cells aged
- BMS regulation outside calibration
Symptoms
- Check-engine or hybrid-system warning light may be on
- Reduced power or limited vehicle operation
- Reduced electric driving range or hybrid assist
How to diagnose it
- Read freeze-frame data and hybrid-system fault codes to see when voltage fell low and whether related battery or isolation faults were recorded.
- Use a compatible scan tool to compare pack voltage and battery-section readings under the conditions captured in the freeze frame, following the manufacturer's procedures.
- Check the 12-volt battery condition and relevant low-voltage connections, since unstable control-system power can affect battery monitoring.
- Have the high-voltage battery and its connections assessed with the manufacturer's safety procedures and specified tests; do not probe high-voltage components yourself.
- If battery readings are plausible but the fault returns, check battery-management system data and control operation against the manufacturer's specification.
Common fixes
- Repair a confirmed low-voltage supply or connection problem affecting battery control.
- Repair a verified high-voltage battery connection fault using the required safety procedures.
- Replace a battery module or pack only if testing confirms degraded cells are causing low system voltage.
- Repair or update battery-management system control as directed by manufacturer diagnostics.
Can I keep driving?
Avoid long trips, hard acceleration, and relying on electric range or hybrid assist; the vehicle may reduce power or enter limited operation. If power drops sharply or a high-voltage warning appears, stop safely and have the vehicle assessed by a qualified hybrid technician.
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.