What it means
The HV battery pack coolant pump B reports a overspeed /air in system condition. Battery thermal management may be impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Battery coolant pump B circulates coolant through part of the high-voltage battery’s thermal-management loop. This code indicates that pump B’s reported speed is higher than expected or that air in the loop is disrupting the pump’s operation, so battery cooling may be unreliable.
Common causes
Most likely first.
- Air in the coolant loop
- Coolant level low
- Pump speed feedback fault
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
- Save freeze-frame data and use a compatible scan tool to compare pump B’s commanded and reported speeds with battery temperatures.
- Check the coolant level and look for leaks in the battery-cooling loop, following the vehicle’s safety procedure.
- Inspect accessible pump B wiring and connectors for damage or a poor connection that could distort speed feedback, without disturbing high-voltage components.
- Check the loop for signs of air or interrupted coolant flow and follow the vehicle’s specified filling and bleeding procedure if indicated.
- If coolant level and flow are correct, test pump B’s speed feedback and operation against the manufacturer’s procedure.
Common fixes
- Repair a coolant leak and restore the specified coolant level.
- Remove air from the battery-cooling loop using the vehicle’s specified procedure.
- Repair a loose or damaged pump B speed-feedback connection or wiring.
- Replace pump B if its speed feedback is faulty or it operates abnormally with a properly filled loop.
Can I keep driving?
Avoid fast charging, hard driving, and long trips until pump B operation and coolant flow are checked. If the hybrid or EV system reports a battery-temperature warning or limits power, stop safely and arrange assistance.
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.