Engine Coolant Temperature Too High

The engine is overheating due to a coolant issue, which means the temperature sensor is reading higher than normal, leading to potential engine damage if not resolved quickly.

The engine control unit (ECU) monitors the engine coolant temperature from the sensor. If it reads above a predefined threshold (usually around 240°F or 115°C), it triggers 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. If it's low, fill it with the appropriate coolant and check for leaks. If coolant is leaking, repair it. Decision: If coolant was low and leaks are fixed, clear the code and test drive. Did the code return? Yes: Proceed to next step. No: Job done.
2. 22. Inspect the hoses for any blockages or kinks. Ensure there are no air pockets in the cooling system. Decision: Is airflow to the radiator blocked? Yes: Clear obstruction. No: Proceed to next step.
3. 33. Check the operation of the thermostat by monitoring engine temperature as it heats up. The thermostat should open at the specified operating temperature. Decision: Is the thermostat operating properly? Yes: Proceed to next step. No: Replace thermostat.
4. 44. Test the coolant temperature sensor with a multimeter. Measure the resistance at various temperatures and compare with the manufacturer's specifications. Decision: Is the sensor reading accurately? Yes: Inspect the engine cooling fan operation. No: Replace the sensor.
5. 55. If all components check out, inspect for internal engine issues that might be causing overheating, like head gasket failure or coolant passages blockage.

• Low coolant level
• Coolant leaks
• Thermostat stuck closed
• Faulty coolant temperature sensor
• Cooling system blockage

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