Engine Coolant Temperature Sensor 1 Out of Range

Your engine's computer is reading a coolant temperature that's too high or too low, which can indicate a problem with the sensor or the actual coolant temperature.

The engine control module (ECM) reads coolant temperature from the sensor. Normally it should see a temperature between 190°F to 220°F (88°C to 104°C) when engine is at operating temperature. If the sensor gives a reading that is higher than 250°F (121°C) or lower than 50°F (10°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 coolant level—should be within specified range; top it off if low before further testing.
2. 22. Inspect wiring and connectors of the coolant temperature sensor. Look for frayed wires or corrosion; repair or replace as necessary.
3. 33. Use a scan tool to monitor the coolant temperature reading. Compare it to an infrared thermometer reading at the thermostat housing—should match closely.
4. 44. If readings are still out of range, replace the coolant temperature sensor and check for any changes in the code.

• Faulty coolant temperature sensor
• Wiring issues (shorts, open circuits)
• Coolant leaks affecting actual temperature
• Incorrect coolant level/mixture

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