What it means
The DC/DC converter step-down (buck) voltage performance is outside calibration. Output voltage does not match commanded value.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The DC/DC converter's step-down function converts higher-voltage hybrid or EV power to the lower voltage used by the 12-volt electrical system. The control module compares the commanded step-down output with the measured result, and this code sets when that output does not track the command within the vehicle's calibration.
Common causes
Most likely first.
- Regulator characteristic drifted
- Load mismatch
Symptoms
- Check-engine or hybrid-system warning light on
- Charging-system warning light may come on
- 12-volt electrical system performance may be affected
How to diagnose it
- Record freeze-frame data and check whether the mismatch occurred during charging, heavy 12-volt electrical load, or a change in vehicle operating state.
- Use a scan tool to compare commanded and actual step-down output and review related 12-volt charging data.
- Inspect the converter's accessible low-voltage connectors, grounds, and wiring for looseness, corrosion, heat damage, or poor contact.
- Check the 12-volt battery condition and connected loads for a load mismatch that could affect converter output.
- Test the step-down circuit and converter response under the conditions specified in service information, comparing measurements with the manufacturer's specification.
Common fixes
- Clean and secure a loose or corroded low-voltage connector or ground.
- Repair damaged wiring in the converter's step-down control or output circuit.
- Correct a weak 12-volt battery or abnormal electrical load if testing identifies it as the mismatch source.
- Replace the DC/DC converter if its step-down output remains outside specification with sound wiring and appropriate loads.
Can I keep driving?
Avoid long trips if the charging warning appears or 12-volt systems behave erratically, since the low-voltage battery may not be replenished properly. If power is reduced or electrical functions become unreliable, stop safely and have the hybrid system checked.
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.