Engine Coolant Temperature Too High

The computer is saying that the engine is getting too hot—above about 240 degrees Fahrenheit—because the coolant can't cool it down enough.

The engine control module (ECM) monitors coolant temperature through a sensor, expecting readings typically in the range of 190°F to 220°F (88°C to 104°C). If it sees temperatures over 240°F (116°C) for 20 seconds or more, it sets this code.

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 the coolant level in the reservoir and radiator. Ensure it's at the proper level. Decision: If low, top it off and retest.
2. 22. Inspect coolant for leaks around hoses, radiator, and engine block. Decision: If leaks are found, fix them and retest.
3. 33. Test the coolant temperature sensor with a multimeter, checking for proper resistance values (typically 2.5kΩ at 68°F / 20°C and around 350Ω at 212°F / 100°C). Decision: If the sensor is out of spec, replace it.
4. 44. Check the operation of the thermostat by monitoring engine temperature while running. If engine does not reach operating temp or overheats, replace the thermostat. Decision: If it does not open, replace it.
5. 55. Inspect the water pump for proper operation; check for leaks or noise. Decision: If it's defective, replace the water pump.

• Low coolant level
• Faulty coolant temperature sensor
• Coolant leaks
• Ineffective water pump operation
• Clogged radiator
• Thermostat stuck closed

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