Diagnostic Event: Engine Cooling System Performance

You're dealing with an engine cooling issue, which might make the engine run too hot and damage parts if not fixed.

The ECM is monitoring coolant temperature and flow; if it detects that the engine isn't cooling properly (usually if it sees temperatures exceeding 220°F for too long), it triggers this fault.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check coolant level in the reservoir; it should be between the minimum and maximum marks. If low, refill and recheck for leaks. Decision: If level is low, address the leak and retest. If level is okay, continue to Step 2.
2. 22. Inspect the condition of the radiator and hoses. Look for blockages or leaks that could affect flow. Decision: If clear but hot under load, go to Step 3. If blocked or leaking, fix the issue and retest.
3. 33. Verify operation of the thermostat by checking the temperature at the upper radiator hose. It should open at around 195°F-203°F. Decision: If stuck closed, replace thermostat. If opens as expected, proceed to Step 4.
4. 44. Test the water pump operation. Ensure it is circulating coolant properly - look for leaks, noise, or wobbling. Decision: If it’s not circulating, replace the water pump. If it’s working, go to Step 5.
5. 55. Check the electrical connector and wiring for the coolant temperature sensor. Ensure it is securely attached, with no signs of corrosion or damage. Decision: If issues are found, repair/replace the connector. If wiring looks good, consider a faulty sensor.

• Low coolant level
• Clogged radiator
• Faulty thermostat
• Failed water pump
• Electrical issues with temperature sensor

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