Engine Coolant Temperature Too High

The engine's computer monitors the engine coolant temperature, and if it sees that the temperature exceeds a predetermined threshold (typically over 240°F or 115°C), it triggers this code to prevent overheating.

The engine control unit (ECU) expects a coolant temperature between 180°F and 220°F (82°C to 104°C) in normal operating conditions. If it detects coolant temperatures above 240°F (115°C), the code is set.

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; it should be within the 'full' range. If low, top it off and check for leaks. Decision: If low, fill and retest. If not low, proceed to step 2.
2. 22. Inspect the coolant temperature sensor connector for corrosion or damage. Make sure it’s securely plugged in. Decision: If damaged, repair or replace the connector. If connector is fine, proceed to step 3.
3. 33. Use a scan tool to read the live data for the coolant temperature. Compare the value with an infrared thermometer directly on the engine block near the thermostat housing. Decision: If readings differ significantly (more than 10°F or 5°C), consider replacing the coolant temperature sensor. If readings are similar, proceed to step 4.
4. 44. Check the operation of the thermostat by observing engine warm-up times. An engine that warms up too slowly may indicate a stuck-open thermostat. Decision: If the thermostat is faulty, replace it. If it functions properly, proceed to step 5.
5. 55. Inspect the radiator for blockages or obstructions and check fan operation. The fan should engage when the coolant temperature exceeds 220°F (104°C). Decision: If the fan doesn’t operate, test/replace it.

• Low coolant level
• Faulty thermostat
• Blocked radiator
• Failed coolant temperature sensor
• Water pump failure

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