What it means
The first coolant pump runs even when no command is active. Driver is stuck on or the wire is shorted to a permanent supply.
At a glance
- Usually lights the check-engine light
How it works
Coolant Pump A is the first electric pump in a vehicle's cooling system and may serve a different loop from Pump B. P261F sets when Pump A runs despite having no active command, which can point to a stuck controller driver, a control wire shorted to permanent battery power, or a pump that sticks mechanically.
Common causes
Most likely first.
- ECU output driver stuck on
- Control wire shorted to a permanent B+ supply
- Carbon or debris buildup preventing free movement
Symptoms
- Check-engine light
- Pump may continue running after the engine is off
- Battery may discharge if the pump keeps running
How to diagnose it
- Review freeze-frame data and live pump-command status to confirm whether Pump A was commanded off when the fault set.
- After shutdown, check whether Pump A continues running beyond the vehicle's normal cool-down behavior.
- Inspect Pump A's control wiring and connector for damage, corrosion, or a short to a permanent power feed.
- Use the wiring diagram and manufacturer's procedure to check whether the controller output remains powered when Pump A is commanded off.
- If power is removed as commanded but Pump A keeps running, check for a mechanical sticking fault in the pump.
Common fixes
- Repair Pump A wiring shorted to permanent battery power.
- Clean and secure corroded or loose Pump A connector terminals.
- Repair or replace the controller if its Pump A output is confirmed stuck on.
- Repair or replace Pump A if it mechanically sticks on.
Can I keep driving?
If Pump A continues running after its normal shutdown period, monitor the battery and avoid leaving the vehicle parked for a long time until diagnosed. The pump can drain the battery, and a fault affecting its cooling loop may also cause temperature problems.
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.