ECM - Engine Over Temperature

The engine computer has noticed that the coolant temperature is above the normal range, meaning the engine may be overheating and could be damaging components.

The ECM monitors the coolant temperature through a sensor, expecting it to stay typically between 190°F and 220°F (88°C to 104°C). If the reading exceeds this range significantly, the fault code triggers.

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; top off if low. Decision: If low, refill and retest. If normal, proceed to next step.
2. 22. Inspect for any visible coolant leaks under the vehicle or around the engine. Decision: If leaks are found, repair and retest. If none, proceed to next step.
3. 33. Measure the coolant temperature using a scan tool. Check if it's above 230°F (110°C) when the engine is at operating temperature. Decision: If yes, proceed to next step; if no, look for potential intermittent issues and monitor.
4. 44. Test the thermostat by checking if the engine warms up correctly and the radiator hoses get hot as the engine heats up. Decision: Replace the thermostat if it doesn't open. If it's functioning, proceed to next step.
5. 55. Check the coolant temperature sensor's signal and resistance at various temps. Expected value at 200°F (93°C) should be around 2.5k ohms. Decision: Replace the sensor if out of range. If sensor is good, further check the cooling system components.

• Low coolant level
• Thermostat stuck closed
• Coolant leaks
• Faulty coolant temperature sensor
• Radiator issues

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