Engine Coolant Temperature Sensor Failure
The engine coolant temperature sensor is malfunctioning or reporting an incorrect temperature.
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What it means (plain English)
The engine coolant temperature sensor measures the temperature of the coolant in the engine. If it's faulty, the computer doesn't know how hot the engine is, which can lead to issues like overheating or poor fuel mix.
What the computer is actually seeing
The engine control module (ECM) expects a coolant temperature between 180°F and 220°F during normal operation. If the sensor reads below 100°F or above 250°F, or reports erratic voltages, it flags this code.
What a healthy reading looks like
Expected coolant temperature readings should be between 180°F (82°C) to 220°F (104°C) while engine is running at operating temperature.
Guided diagnostic — the DiagCoach way
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.
- 11. Check the wiring and connector for the coolant temperature sensor for any damage or corrosion. Repair as needed. Decision: Are there any issues? If yes, fix them before proceeding.
- 22. Measure the resistance of the coolant temperature sensor at room temperature. It should read approximately 2.5k ohms at 77°F (25°C). Decision: Is the resistance value within range? If no, replace the sensor.
- 33. Start the engine and allow it to reach normal operating temperature. Monitor the coolant temperature reading on the scan tool. Decision: Is the reading consistent with the actual engine temperature? If no, replace the sensor or check the ECM.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues (frayed/corroded connections)
- Connector problems (loose/corroded pins)
- Faulty ECM
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix this soon since it can lead to overheating or poor engine performance.
Will this issue come back after repair?
If the root cause is correctly identified and repaired, it should not return.
Why does this code pair with others?
Engine temperature influences many systems, so issues with temperature sensors often affect fuel mixture and emissions systems.
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