What it means
Hybrid/EV electronics coolant pump B reports a performance condition. Power electronics cooling on this branch is impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Electronics coolant pump B circulates coolant through a specific hybrid or EV power-electronics branch. The control module sees that pump B’s cooling performance does not match the command or expected thermal response, even though the circuit may not be fully open.
Common causes
Most likely first.
- Pump motor or driver fault
- Air or coolant level issue
Symptoms
- Check-engine or hybrid-system warning light
- Reduced power or limited hybrid operation
- Possible power-electronics overheating warning
How to diagnose it
- Capture freeze-frame data and compare pump B command and status with the temperatures on its cooling branch.
- Check the electronics-coolant level and inspect the pump B branch for leaks, trapped air, or restricted flow using the manufacturer’s procedure.
- Inspect pump B’s connector and harness for looseness, corrosion, or damage that could cause weak or intermittent operation.
- Run the prescribed pump B activation test and observe whether coolant circulates and branch temperatures respond as expected.
- If flow is poor despite sound wiring and correct coolant level, test the pump motor and driver against the manufacturer’s specification.
Common fixes
- Correct low coolant, leaks, or air in the pump B branch using the specified filling and bleeding procedure.
- Repair loose or corroded pump B electrical connections.
- Replace pump B if it runs weakly or fails the prescribed activation test.
- Repair a confirmed pump driver or flow restriction affecting pump B’s branch.
Can I keep driving?
Avoid high loads and long trips because inadequate pump B flow can overheat power electronics and trigger reduced power. Stop if an overheating warning appears or power drops sharply.
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.