What it means
The DC/DC converter B temperature has exceeded the permitted limit. The control module sets this code when monitored converter temperature remains above its calibrated threshold.
How it works
DC/DC converter B converts high-voltage battery power into low-voltage power for the vehicle’s 12-volt system, and it must shed heat while operating. The control module monitors converter B temperature and sets this code when it stays above its allowed threshold, which can prompt power or charging limits to protect the equipment.
Common causes
Most likely first.
- Restricted coolant flow or failed cooling pump
- Blocked heat exchanger or airflow
- Low coolant level
- Faulty temperature sensor
Symptoms
- Hybrid or EV warning light
- Reduced power
- 12-volt charging warning
- Cooling fan may run more often
How to diagnose it
- Record freeze-frame data and check live data for converter B temperature, noting whether it rose with load or remained high after the vehicle cooled.
- Check for related cooling-system or converter codes and inspect the coolant level only when the system is cool and according to the owner’s manual.
- Look for visible leaks or blocked airflow around the converter B cooling path and its heat exchanger.
- Check whether the cooling pump and fans operate as expected using the manufacturer’s diagnostic procedure; do not touch high-voltage components.
- If coolant flow and airflow are adequate, test the converter B temperature sensor and compare its reading with the manufacturer’s procedure and specification.
Common fixes
- Top up the correct coolant if the level is low and no unsafe leak is present, following the owner’s manual.
- Clear debris or obstruction from the converter B heat exchanger and airflow path.
- Repair a failed cooling pump or blocked coolant passage after confirming the fault.
- Repair a coolant leak and refill or bleed the circuit as specified by the manufacturer.
- Replace the temperature sensor if it reports incorrectly while converter B is cool and the circuit checks out.
Can I keep driving?
Reduce load and stop safely if a temperature warning appears, power drops, or the 12-volt charging warning comes on; do not continue driving an overheating converter. Continued overheating can force reduced power and may damage the converter or interrupt low-voltage charging.
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.