What it means
The HV battery pack coolant heater B reports a control performance condition. Battery preheating may be impaired in cold weather.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Battery coolant heater B warms the coolant used to condition the high-voltage battery, particularly before or during cold-weather operation. The control module compares heater B's commanded operation with its electrical or heating response and sets P0E19 when performance falls outside the expected range, even if the circuit is not simply open or shorted.
Common causes
Most likely first.
- Heater element output degraded
- Low supply voltage under load
- Fault in heater control circuit
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 and hybrid-system live data for the battery temperature, heater B command, supply conditions, and whether the fault occurred during a heating request.
- Inspect heater B's wiring, connectors, and accessible coolant connections for damage, poor contact, or signs that coolant flow or heating is impaired.
- Check the vehicle's low-voltage supply condition and measure heater B circuit supply under load using the manufacturer's procedure.
- Test heater B's control circuit and element for faults that could reduce output while remaining electrically connected.
- Compare heater B's operation and coolant or temperature response with the manufacturer's diagnostic criteria to distinguish a degraded element from a control-circuit fault.
Common fixes
- Repair a loose or damaged heater B connector or wiring fault.
- Restore a weak supply connection that causes voltage to drop under load.
- Repair a heater B control-circuit fault identified by testing.
- Replace heater B if its output is below the manufacturer's specification.
Can I keep driving?
The vehicle may charge more slowly, lose electric range, or limit power if the battery cannot be warmed as expected. Use gentle driving and avoid relying on full electric performance in cold conditions until heater B's operation is restored.
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.