Cooling System Performance

The computer is detecting a problem with how the engine is cooling itself, which could lead to overheating if not addressed.

The computer monitors coolant temperature and compares it to expected values during operation. If the coolant temperature is too high (usually above 230°F) or varies excessively from normal operating temperature, it throws 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 coolant level in the reservoir. If low, top off and check for leaks. Decision: Did this fix the issue? If yes, you're done. If no, proceed to the next step.
2. 22. Inspect the coolant for contamination or leaks. Look for any visible signs of coolant leakage around hoses and the radiator. Decision: Is there a leak? If yes, repair the leak. If no, proceed to the next step.
3. 33. Check the thermostat operation. Remove the thermostat and test it in hot water to ensure it opens at the correct temperature (typically 195°F). Decision: Does it open? If yes, replace with a new thermostat and retest. If no, replace the thermostat.
4. 44. Verify the cooling fan operation by checking if it turns on when the coolant reaches 220°F. Decision: Is the fan operating properly? If no, check the fan relay and wiring. If yes, proceed to the next step.
5. 55. Test the temperature sensor in the cooling system using a multimeter. Resistance should change accurately with temperature. Decision: Is the sensor working within spec? If no, replace the sensor. If yes, inspect the engine for underlying issues.

• Low coolant level
• Coolant leaks
• Failed thermostat
• Cooling fan malfunction
• Clogged radiator
• Faulty temperature sensor

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