P0E1A: Hybrid/EV Battery Pack Coolant Pump B Control Circuit/Open
What to do
Expect slower rapid charging and reduced power in hot weather. If the car has recently had coolant or battery work, mention it — trapped air is a common cause and costs nothing to fix, whereas a pump does not.
What this code means
The control circuit for the second traction battery coolant pump is faulty.
A second pump means the pack's thermal circuit has two loops or needs more flow than one pump provides, and the consequence is that losing one is a partial failure rather than a total one — which makes it harder to spot, not easier. Cooling continues at reduced capacity, so the pack still works and simply derates sooner than it used to.
The symptom is therefore seasonal and gradual: rapid charging that has become slower, and power that fades on a long climb or a hot day. Neither is dramatic, and both get attributed to the battery ageing.
Air in the circuit deserves ruling out first if the car has had recent coolant work. An electric vehicle's thermal system has several loops and high points, and an airlock stops flow completely while the pump runs perfectly — the pump is then the symptom rather than the fault, and replacing it changes nothing.
The control circuit is open — no drive reaching the pump.
Likely causes
Start here
- Faulty inverter coolant pump · specialist
- Air trapped in the inverter cooling circuit · moderate
- Corroded or loose connector · specialist
Less common
- Low inverter coolant level · moderate
- Open circuit in control wiring · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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