Engine Temperature Sensor 1
Indicates a high temperature reading from the engine coolant temperature sensor.
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What it means (plain English)
The engine coolant temperature sensor measures how hot the engine is running. If this sensor sends a signal that the temperature is too high, it means the engine might be overheating or the sensor itself is faulty.
What the computer is actually seeing
The engine control module (ECM) is expecting a voltage signal between 0.5V (cold) and 4.5V (hot). If it sees a voltage higher than 4.5V, it triggers a fault code. This could happen due to high coolant temperature or sensor failure.
What a healthy reading looks like
Coolant temperature typically ranges from 185°F to 220°F (85°C to 104°C) during normal operation. Above 240°F (115°C) may trigger this code.
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 coolant level in the reservoir. If low, top off and recheck the code after driving.
- 22. Inspect wiring and connectors to the engine coolant temperature sensor for damage or corrosion. Repair as necessary.
- 33. Measure voltage at the engine coolant temperature sensor connector with the engine running. Expected should be between 0.5V and 4.5V—anything outside indicates a sensor issue.
- 44. If voltage is out of range, replace the engine coolant temperature sensor and clear the codes.
- 55. If the sensor is good, check engine operation temperatures with a scan tool during normal operation.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues (short circuit, high resistance)
- Low coolant level
- Cooling system blockage
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity means it's best to fix soon, but you can drive it short distances unless overheating occurs.
Will this code come back?
It may come back if the underlying issue isn't resolved, like a bad sensor or low coolant.
Why does it sometimes pair with other codes?
Issues with the coolant temperature can affect various systems, triggering related fault codes.
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