What it means
The motor electronics coolant pump B is not meeting the expected performance monitored by the control system. The reason may involve the pump or coolant flow, and varies by vehicle.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Motor electronics coolant pump B moves coolant through a power-electronics cooling circuit; its location and circuit differ by vehicle. The control system monitors pump B and its cooling performance, setting this code when the expected operation is not achieved.
Common causes
Most likely first.
- Air in the coolant circuit
- Low coolant level
- Restricted coolant flow
- Faulty coolant pump
- Pump wiring or connector fault
Symptoms
- Hybrid or powertrain warning light
- Reduced vehicle power
- Possible overheating of motor electronics
How to diagnose it
- Use a hybrid-capable scan tool to review freeze-frame data and live pump B and temperature information for the conditions that triggered the fault.
- With the system cool, check the coolant level for pump B's circuit and inspect for leaks or evidence of air.
- Inspect pump B's connector and accessible wiring for looseness, corrosion, or physical damage.
- Check pump B hoses and passages for restriction, and bleed the circuit only by the manufacturer's procedure if air is indicated.
- If coolant flow and wiring appear sound, test pump B using the manufacturer's procedure and replace it if it fails.
Common fixes
- Correct a low coolant level and repair the source of any leak.
- Bleed air from pump B's circuit according to the manufacturer's procedure.
- Repair damaged wiring, a poor connector, or a restricted hose serving pump B.
- Replace pump B if its performance test fails.
Can I keep driving?
Because pump B may be failing to cool motor electronics, avoid driving if power is reduced or an overheating warning appears; continued use can cause heat damage. Stop safely if those symptoms occur and have the cooling fault checked.
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.