Engine Coolant Temperature Sensor 1 High
The engine coolant temperature sensor is reporting a high temperature reading.
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What it means (plain English)
The engine's computer thinks the coolant is way too hot, which can trigger overheating prevention measures and could damage the engine.
What the computer is actually seeing
The engine control unit (ECU) is receiving a signal from the coolant temperature sensor indicating temperatures above 250°F (121°C), which is outside the normal operating range.
What a healthy reading looks like
Normal coolant temperature should be around 180°F to 220°F (82°C to 104°C).
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 coolant level in the reservoir and radiator. Ensure it's at the proper level and not leaking.
- 22. Inspect the wiring and connectors at the coolant temperature sensor for damage or corrosion.
- 33. Use a scan tool to check the live data from the coolant temperature sensor. If the reading is above 250°F (121°C) while the engine is cool, the sensor is likely faulty.
- 44. Replace the coolant temperature sensor if it's giving continuously high values. Test the new sensor before reassembly.
- 55. If the problem persists, check the thermostat and ensure it opens at the correct temperature, typically around 185°F (85°C).
Common causes
- Faulty coolant temperature sensor
- Wiring issue or short in the sensor circuit
- Coolant level too low
- Thermostat stuck closed
- Air trapped in the cooling system
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, it can lead to overheating and engine damage. Address it immediately.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code will likely return.
Why does this code sometimes pair with SPN 110?
SPN 110 indicates the same sensor might be malfunctioning or reading improperly.
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