Excessive Engine Coolant Temperature

The engine's coolant is getting too hot, which can cause overheating and damage. This means the cooling system isn't working right, or the engine is generating too much heat without being cooled down efficiently.

The engine control unit (ECU) detects that the coolant temperature has exceeded 250°F (121°C) for too long, triggering a fault 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. 1Check coolant level in the reservoir; refill if low and inspect for leaks. Decision: If level was low, check for leaks.
2. 2Inspect the thermostat operation: remove and test by placing it in boiling water; it should open fully. Decision: Replace if it doesn't open at 195°F (91°C).
3. 3Check the radiator for blockages; clean if necessary. Decision: Replace if significant debris is found.
4. 4Test the water pump by checking for coolant flow from the radiator when engine is hot; replace if no flow is observed. Decision: Replace water pump if flow is inadequate.
5. 5Check the coolant temperature sensor output using a multimeter; should match the engine temperature. Decision: Replace the sensor if readings are inconsistent with actual temperature.

• Low coolant level due to leaks or evaporation.
• Faulty thermostat stuck closed.
• Blocked radiator or coolant passages.
• Failed water pump not circulating coolant properly.
• Faulty coolant temperature sensor.

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