What it means
During cold start, the engine coolant pump does not produce the expected flow. Pump aging combined with high cold viscosity, or pump-disable strategy malfunction.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The engine coolant pump circulates coolant through the engine and, on some vehicles, through the heater circuit. During a cold start, the control module detects that pump performance or coolant flow is below what it expects, which can delay warm-up and cabin heat.
Common causes
Most likely first.
- Pump output degraded with age
- Cold coolant viscosity too high
Symptoms
- Check-engine light
- Longer warm-up time
- Heater takes longer to produce warm air
How to diagnose it
- Review freeze-frame data and cold-start live temperature readings to confirm the fault occurs during the initial warm-up period.
- Check the coolant level when the engine is fully cold and inspect for leaks or signs of incorrect or degraded coolant.
- Inspect the coolant pump, its drive or electrical connection as applicable, and visible coolant hoses for damage or restriction.
- Compare pump operation and coolant temperature change during a cold start with the manufacturer's diagnostic procedure.
- If coolant condition and visible flow paths are sound, test the pump and its control strategy to determine whether output is weak or operation is being inhibited.
Common fixes
- Correct a low coolant level and repair any leak using the specified coolant.
- Replace aged or incorrect coolant with the specified type and mixture if its condition is responsible for poor cold flow.
- Repair the pump's electrical connection or control fault if the pump is not being commanded or powered correctly.
- Replace the coolant pump if testing confirms degraded cold-start flow.
Can I keep driving?
Avoid driving if the temperature warning appears, the engine overheats, or coolant is leaking; overheating can quickly damage the engine. If temperature stays normal, a short trip may be possible, but monitor it closely and expect delayed cabin heat.
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.