What it means
The auxiliary cooling system is not performing as expected. The module sets this code when monitored temperatures or cooling behavior do not meet the system's expected performance criteria.
How it works
The auxiliary cooling system circulates coolant to remove heat from components such as the converter and other hybrid or electric-drive equipment. The control module evaluates system temperatures and cooling behavior; this code sets when the observed cooling performance does not meet the system’s expected response, even if one specific part has not yet been identified as the cause.
Common causes
Most likely first.
- Low coolant level
- Failed auxiliary coolant pump
- Blocked coolant passage or heat exchanger
- Air trapped in the cooling circuit
Symptoms
- Hybrid or EV warning light
- Reduced power
- Temperature warning
- Cooling fan may run more often
How to diagnose it
- Record freeze-frame data and check live coolant-temperature data to see which temperature rose and under what operating conditions.
- When the system is cool, check the auxiliary coolant level and look for visible leaks, following the owner’s manual.
- Inspect accessible auxiliary cooling passages and heat exchangers for blockage or debris that could restrict heat transfer.
- Check auxiliary pump operation and coolant circulation using the manufacturer’s diagnostic procedure.
- If level, circulation, and airflow appear normal, have the circuit checked for trapped air or internal restriction using the manufacturer’s procedure.
Common fixes
- Correct a low coolant level with the specified coolant and investigate any leak.
- Remove debris blocking the auxiliary heat exchanger or airflow path.
- Replace a failed auxiliary coolant pump after confirming it does not circulate coolant correctly.
- Repair a blocked passage or leaking hose in the auxiliary cooling circuit.
- Bleed trapped air from the auxiliary circuit using the manufacturer’s procedure.
Can I keep driving?
Reduce load and stop safely if a temperature warning appears or power is reduced, especially if temperatures continue rising. Poor auxiliary cooling can lead to overheating and protective limits on hybrid or electric drive.
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.