Engine Coolant Temperature Too High

The computer is reading that the engine coolant temperature is too high, which can mean it’s not cooling properly. Typically, normal engine temperature should be around 190°F to 220°F. If it goes over about 240°F, you might have overheating issues.

The engine control module (ECM) measures the coolant temperature through a sensor that sends voltages between 0.5V (cold) and 4.5V (hot). If the voltage exceeds 4.5V, the ECM determines the coolant temperature is too high and sets the 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 and radiator. If low, top off and retest. Decision: If code returns, proceed to step 2.
2. 2Inspect coolant temperature sensor wiring and connector for damage or corrosion. Repair if needed.
3. 3Test the coolant temperature sensor with a multimeter to ensure it’s sending correct voltage outputs (should be 0.5V at 32°F and about 4.5V at 250°F). If readings are incorrect, replace the sensor. Decision: If code returns, continue to step 4.
4. 4Check the thermostat operation. It should open at the correct temperature (usually around 195°F). If it’s stuck closed, replace the thermostat. Decision: If code still appears, proceed to the next step.
5. 5Inspect the radiator for blockages, dirt, or debris affecting airflow. Clean as necessary. Decision: If all checks are okay but code persists, consider the water pump.

• Low coolant level
• Faulty coolant temperature sensor
• Bad thermostat
• Blocked radiator
• Failed water pump

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