What it means
The controller cannot drive the third electric coolant pump. Cooling demand of the connected loop (often hybrid power electronics or battery cooling) is not satisfied.
At a glance
- Usually lights the check-engine light
How it works
Coolant pump C moves coolant through a third electrically controlled cooling loop, which may serve powertrain electronics or a battery system. The controller monitors the pump's electrical circuit and sets P26F4 when it detects an open path that prevents it from driving the pump.
Common causes
Most likely first.
- Open pump motor winding
- Broken control wire to the pump
Symptoms
- Engine or powertrain warning light may come on
- Temperature warning may appear if the affected cooling loop overheats
- Cooling performance may be reduced in the affected system
How to diagnose it
- Record freeze-frame data and check temperature readings for the system served by pump C to see whether the fault coincided with rising temperatures.
- Inspect pump C's connector and nearby harness for disconnection, broken wires, corrosion, or heat damage.
- Check the pump circuit fuse, power, and ground according to the manufacturer's wiring information.
- With power isolated as specified by the manufacturer, test the pump C wiring for continuity and the motor winding for an open.
- If the wiring and winding pass, check the controller's pump C output and commanded operation using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect pump C and secure its harness if the connector has come loose.
- Repair a broken wire or corroded terminal in the pump C circuit.
- Replace a failed fuse after finding and correcting the cause of the open circuit.
- Replace pump C if its motor winding is confirmed open.
- Repair the controller output circuit if testing confirms it cannot drive the pump.
Can I keep driving?
If a temperature warning appears, the affected cooling system overheats, or the vehicle limits power, stop safely and switch off the vehicle; continued operation can damage the engine, battery, or power electronics. Without those signs, avoid heavy loads and long trips until pump C is 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.