What it means
The controller cannot drive the second electric coolant pump (B). Often used for aftertreatment, turbo cool-down, or hybrid battery loops — fault stops circulation in that loop.
At a glance
- Usually lights the check-engine light
How it works
Coolant Pump B is a second electrically driven pump that circulates coolant through a separate vehicle-specific loop, such as an aftertreatment, turbo cool-down, or hybrid battery loop. The controller monitors the pump's control circuit and sets P261A when it detects an open circuit that prevents it from driving Pump B.
Common causes
Most likely first.
- Open pump motor winding
- Broken control wire to the pump
Symptoms
- Check-engine light
- Possible overheating or reduced cooling in the loop served by the pump
How to diagnose it
- Use freeze-frame data and the vehicle's service information to identify which cooling loop Pump B serves and whether it was being requested when the code set.
- With the system safely cool, inspect Pump B's connector and control-wire route for loose pins, corrosion, chafing, or a broken wire.
- Check the pump winding and control-wire continuity using the manufacturer's procedure and specifications.
- Check that the controller's command and power supply reach the pump circuit as specified.
- If the wiring and supply are intact but the winding is open, confirm the pump has failed before replacing it.
Common fixes
- Reconnect or clean a loose or corroded Pump B connector.
- Repair a broken control wire or terminal in the Pump B circuit.
- Replace Pump B if its motor winding is confirmed open.
Can I keep driving?
Avoid driving if the loop served by Pump B is overheating or showing a temperature warning; otherwise, keep trips short and monitor temperature until diagnosed. Loss of circulation can overheat that specific loop and damage the equipment it cools.
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.