What it means
The supply voltage circuit of the HV battery pack cooling fan reports a circuit low condition. Cooling fan operation may be impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The hybrid battery cooling fan depends on a supply circuit to power airflow through the battery pack. P0BC0 sets when the monitored supply voltage is lower than expected, which can prevent the fan from cooling the pack adequately.
Common causes
Most likely first.
- Wire shorted to ground
- Supply rail collapsed
- Connector pins corroded - high contact resistance
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
- Check freeze-frame data and live fan-command and supply readings to see when the voltage drops and whether the fan is being commanded on.
- With the vehicle powered down as specified by the manufacturer, inspect the fan supply wiring and connector for a short to ground, corrosion, or heat damage.
- Check the fan supply fuse and feed for signs of a collapsed supply or poor connection.
- Measure the supply circuit under the manufacturer’s specified test conditions to locate a voltage drop or short to ground.
- If the wiring and supply source pass, follow the manufacturer’s procedure to assess the fan and its control circuit.
Common fixes
- Clean and secure corroded fan supply connector contacts.
- Repair a fan supply wire shorted to ground.
- Repair a damaged supply feed or poor connection causing voltage drop.
- Replace a failed fuse after identifying and correcting the cause.
- Repair the fan or control circuit if the supply tests correctly.
Can I keep driving?
Avoid long trips, hard acceleration, and charging when the battery fan supply is low, especially in hot weather. Stop if a battery temperature warning or reduced-power alert appears because inadequate cooling can increase battery heat.
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.