Coolant Temperature Above Normal Operating Range

The engine's computer monitors the coolant temperature to keep the engine from overheating. If it gets too high, usually above 248°F (120°C), the computer throws this code to warn you that the engine is at risk of damage.

The engine control module (ECM) calculates the coolant temperature from the sensor's voltage signal, typically around 0.5V for 32°F (0°C) to 4.5V for 248°F (120°C).

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. First, check the coolant level in the reservoir. Should be at or above the 'minimum' mark. If low, top it off and retest.
2. 22. Inspect the coolant temperature sensor and its connector for damage or corrosion. Ensure the connector is tight and clean. If damaged, replace sensor and retest.
3. 33. Using a scan tool, monitor the coolant temperature reading while the engine is running. If the sensor reading is above 248°F (120°C) but the engine feels cool, the sensor is likely faulty. Replace if needed.
4. 44. Check for coolant leaks in hoses and connections. Repair any leaks found and check if the code persists after correcting the issue.
5. 55. Inspect the thermostat operation by running the engine until warm and checking if the upper radiator hose gets hot. If it remains cold, the thermostat might be stuck closed and needs replacing.

• Faulty coolant temperature sensor
• Coolant system leaks
• Thermostat stuck closed
• Cooling fan failure
• Insufficient coolant level
• Radiator blockage

$$ - $$$ (typically $200 to $600, depending on repairs needed)