What it means
The hybrid battery cooling system B does not maintain target temperatures under load. Coolant flow, radiator fouling, or pump output reduced on this branch.
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 temperatures and cooling performance on hybrid/EV battery cooling branch B while the pack is under load. P2D3F sets when that branch cannot keep the battery within its target temperature range; restricted heat rejection, weak pump flow, or pack imbalance can contribute.
Common causes
Most likely first.
- Radiator fins fouled - reduced heat rejection
- Pump output degraded with age
- 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
- Record freeze-frame data and check battery temperatures, cooling requests, and pump commands when branch B performance is flagged.
- Inspect the branch B radiator or heat exchanger fins and air path for dirt, blockage, or damage that could reduce heat rejection.
- Check the branch B coolant level and accessible hoses and connectors for leaks, kinks, or loose electrical connections.
- Use scan-tool data or the vehicle's supported active tests to compare branch B pump operation and temperature change with other cooling branches.
- Test the branch B pump and its wiring, and review battery cell balance if the cooling hardware operates normally.
Common fixes
- Clean debris from the branch B heat exchanger and restore airflow.
- Repair a leaking, kinked, or poorly connected branch B hose or connector.
- Repair damaged pump wiring or connections.
- Replace a branch B pump that fails the manufacturer's performance check.
- Service battery imbalance if cell data shows it is contributing to localized heat.
Can I keep driving?
Limit driving and avoid heavy acceleration, towing, and repeated fast charging because branch B may not remove battery heat effectively. Stop if a battery temperature warning appears or power drops sharply; continued overheating can cause further power limitation or battery damage.
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.