Excessive Coolant Temperature

The engine is getting too hot because the coolant isn't doing its job. This can happen due to low coolant levels, a stuck thermostat, or a bad water pump.

The engine control module (ECM) detects that the coolant temperature sensor is reporting values above 230°F (110°C) for a certain period, indicating potential overheating conditions.

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 and radiator. Ensure it's at the proper level. Decision: If low, add coolant and retest; if full, proceed.
2. 22. Inspect for visible coolant leaks or damage to hoses and the radiator. Decision: If leaks are found, repair and retest; if not, proceed.
3. 33. Check the function of the thermostat by testing its opening temperature. Measure at the engine and ensure it opens around 195°F (91°C). Decision: If it doesn't open, replace the thermostat and retest; if it does open, proceed.
4. 44. Test the water pump for proper operation. Look for leaks or unusual noises. Decision: If the pump is failing or not circulating coolant, replace and retest; if functioning correctly, proceed.
5. 55. Check the coolant temperature sensor by measuring the resistance at various temperatures. Use a scan tool to compare readings to actual temperature. Decision: If out of spec, replace the sensor; if okay, proceed to the next step.
6. 66. Inspect the engine for restrictions in the cooling system, like clogs. This may need a professional flush. Decision: If obstruction found, clear it and retest; if clear, further diagnostics may be required.

• Low coolant level
• Stuck thermostat
• Failed water pump
• Blocked coolant passages
• Faulty coolant temperature sensor

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