Engine Coolant Temperature Sensor High
Indicates that the engine coolant temperature sensor is reading a value that's too high.
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What it means (plain English)
The engine coolant temperature sensor measures how hot the engine coolant is. If it reads too high, it might mean the coolant is boiling, or the sensor is faulty.
What the computer is actually seeing
The electronic control unit (ECU) sees a coolant temperature reading above the typical range, usually above 240°F (115°C).
What a healthy reading looks like
Coolant temp should be between 180°F (82°C) to 220°F (104°C) under normal operating conditions.
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 engine coolant level; ensure it's at the proper level. If low, refill and see if code returns within a drive cycle.
- 22. Inspect wiring and connectors to the coolant temperature sensor for any damage or corrosion; repair as necessary.
- 33. Use a scan tool to compare the ambient and engine coolant temperatures; if the readings are inconsistent, replace the engine coolant temperature sensor.
- 44. Perform a visual check for any leaks in the cooling system that could cause overheating. Repair any leaks found.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issue or connector corrosion
- Coolant leak leading to air pockets or overheating
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It may be drivable, but keep an eye on temperature gauges. Overheating can lead to engine damage.
Will this code come back?
If the underlying issue isn't fixed, yes, it will likely return after clearing the code.
Why do I see this code with SPN 648 or SPN 649?
These codes are related to coolant temperature sensor function, and can appear together if there are sensor or circuit issues.
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