What it means
The coolant pump A runs above the calibrated maximum speed without producing the expected flow. Indicates air pocket in the coolant loop.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Coolant Pump A circulates coolant through its assigned loop, and the control module compares pump speed with the flow or response it expects. This code sets when Pump A spins faster than its calibrated limit but the loop does not show the expected circulation, commonly because trapped air or low coolant prevents the pump from moving coolant properly.
Common causes
Most likely first.
- Air pocket in coolant loop
- Coolant level low
Symptoms
- Check-engine light
- Coolant temperature may fluctuate or rise
- Cabin heat may be weak or inconsistent
How to diagnose it
- Review freeze-frame data and coolant-temperature readings to see when the pump overspeed and temperature fluctuation occurred.
- With the engine cold, check the coolant level and inspect the loop for visible leaks that could have lowered it.
- Look for signs of trapped air or recent coolant-system service, and bleed the loop using the vehicle manufacturer's procedure.
- Use a scan tool to compare Pump A's commanded and reported speed with coolant-temperature or flow data during operation.
- If the level and bleeding are correct but the mismatch remains, test Pump A and its circuit according to the manufacturer's diagnostic procedure.
Common fixes
- Top up coolant with the specified type after correcting any leak.
- Bleed trapped air from the coolant loop using the manufacturer's procedure.
- Repair a leaking hose, connection, or other loop component causing coolant loss.
- Repair or replace Pump A if testing confirms it cannot circulate coolant as expected.
Can I keep driving?
Avoid driving if the coolant temperature rises, fluctuates sharply, or the vehicle enters reduced-power mode; stop safely and let the engine cool. Continued operation with poor circulation can cause overheating and engine damage.
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.