Engine Coolant Temperature (ECT) Sensor 1

Your truck's computer thinks the engine is too hot, which can happen if the coolant is low or if the sensor is bad.

The engine control module (ECM) reads the temperature from the ECT sensor, which should normally be between 180°F and 220°F under normal operating conditions. If the reading exceeds 240°F, the ECM will throw 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 in the reservoir and radiator. Add if low. Decision: If coolant is low, refill and retest for code. If level is normal, proceed to next step.
2. 22. Inspect the wiring and connections to the ECT sensor for any signs of damage or corrosion. Decision: If damaged, repair wiring/connectors and retest. If intact, proceed to next step.
3. 33. Use a scan tool to read the ECT sensor data while the engine is running. Compare with an infrared thermometer at the thermostat housing. Decision: If readings match within 5°F, sensor is likely good. If readings differ significantly, sensor may be faulty. Replace if necessary.
4. 44. Check thermostat operation by monitoring engine temperature rise. If it does not reach normal operating temperature, thermostat may be stuck closed. Replace if necessary.

• Low coolant level
• Faulty ECT sensor
• Wiring issues to the ECT sensor
• Thermostat stuck closed

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