What it means
The motor electronics coolant pump B control circuit reports a control circuit/open condition. Power electronics cooling cannot be commanded reliably on branch B.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Pump B circulates coolant through the hybrid or EV power electronics, helping control the temperature of components such as the inverter. The control module checks whether it can operate this pump through its control circuit. P0B38 sets when that circuit is detected as open, so pump B cannot be commanded reliably.
Common causes
Most likely first.
- Open in pump control wire
- Open pump motor
- Pin pushed back out of connector body
Symptoms
- Hybrid-system warning light may illuminate
- Reduced power or limited hybrid operation
- Power electronics may overheat or trigger protective shutdown
How to diagnose it
- Use a scan tool to record freeze-frame data and check whether pump B is being commanded, since this shows the conditions when the open was detected.
- Inspect pump B's connector and harness for a backed-out pin, loose fit, damage, or corrosion that could break the circuit.
- With the vehicle made safe according to the manufacturer's high-voltage procedures, check the pump B control wire for continuity and for an open between the pump and its controller.
- Check the pump B motor for an open circuit using the manufacturer's test procedure and compare the result with its specification.
- If the wiring and pump pass, test the controller's pump B output and connector terminals for an open or poor connection.
Common fixes
- Seat the pump B connector and secure any backed-out terminal.
- Repair an open or damaged pump B control wire.
- Clean or repair corroded or loose connector terminals.
- Replace pump B if its motor winding is open.
- Repair the pump control module connection or output if testing identifies it as the source.
Can I keep driving?
Avoid demanding driving, towing, or extended trips because loss of pump B circulation can overheat power electronics and lead to reduced power or protective shutdown. If the vehicle limits power or warns of overheating, stop somewhere safe and arrange service.
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.