What it means
The control module commands the engine coolant pump to operate but detects insufficient pump operation or coolant flow. It sets when the pump fails to run or its performance is below the expected level.
At a glance
- Usually lights the check-engine light
How it works
The engine coolant pump circulates coolant so the engine can shed heat. P26CB sets when the module commands the pump to run but detects inadequate operation or coolant flow, which can occur if the pump is seized, its rotor drive has failed, or debris is restricting movement.
Common causes
Most likely first.
- Pump motor seized by sediment
- Cracked rotor magnet decouples drive
- Carbon or debris buildup preventing free movement
Symptoms
- Check-engine light may be on
- Engine may overheat
- Cooling-system warning may appear
How to diagnose it
- Check the temperature gauge and cooling warnings first; if overheating is present, switch off the engine and let it cool.
- Scan for cooling-system codes and review freeze-frame data and live pump command or feedback to confirm when performance fell short.
- With the engine cool, inspect the pump connector and harness for damage and check for visible leaks or signs of coolant loss.
- Check whether the pump responds when commanded using the manufacturer's diagnostic procedure, keeping clear of moving parts.
- If the electrical supply and command are present, assess the pump for binding, sediment, or rotor-drive failure using the manufacturer's procedure.
Common fixes
- Repair a loose or damaged pump connector or wiring if the pump is not receiving its command.
- Correct a coolant leak or contamination that is contributing to debris in the pump.
- Replace a pump that is seized, binds, or has a failed rotor drive.
- Refill and bleed the cooling system according to the vehicle procedure after pump or coolant-system work.
Can I keep driving?
Stop driving if the engine temperature rises or an overheating warning appears; continued operation with poor coolant flow can damage the engine. Let the engine cool fully before checking coolant, and do not open a hot cooling system.
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.