What it means
Hybrid/EV electronics coolant pump B reports a control circuit low 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 its assigned hybrid or EV power-electronics branch. The control module monitors the pump B control circuit and sets this code when the circuit signal is lower than expected, which can result from a pump or driver fault or high resistance at corroded connector contacts.
Common causes
Most likely first.
- Pump motor or driver fault
- Air or coolant level issue
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine or hybrid-system warning light
- Reduced power or limited hybrid operation
- Possible power-electronics overheating warning
How to diagnose it
- Save freeze-frame data and check pump B command, status, and branch temperature readings.
- Check electronics-coolant level and look for leaks or air in pump B’s cooling branch before attributing the fault to the electrical circuit.
- Inspect pump B’s connector for corrosion, moisture, loose contacts, or terminals with poor seating.
- Measure the pump B control-circuit signal, power, ground, and voltage drop under the manufacturer’s prescribed test conditions.
- If the wiring and connector pass, test the pump motor and driver to determine which is pulling the control circuit low.
Common fixes
- Clean or replace corroded pump B connector terminals and restore a sound connection.
- Repair a damaged control, power, or ground wire causing excessive resistance.
- Correct low coolant, leaks, or air in the pump B branch using the specified procedure.
- Replace pump B or repair its driver only if testing confirms that component is faulty.
Can I keep driving?
Keep loads light and avoid long trips because pump B may not cool its power-electronics branch adequately, leading to overheating or reduced power. Stop if an overheating warning appears.
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.