Coolant Temperature Sensor 1 Out of Range – High
The coolant temperature sensor is reporting a temperature that is too high.
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What it means (plain English)
The coolant temperature sensor is supposed to read the engine's temperature and send that info to the computer. If it sees a number higher than it can handle, like over 250°F (121°C), it triggers this code.
What the computer is actually seeing
The engine control module (ECM) is seeing a voltage signal from the coolant temperature sensor that corresponds to a temperature above what it's expecting, usually over 250°F (121°C).
What a healthy reading looks like
Normal coolant temperature should be between 190°F (88°C) and 220°F (104°C). Above 250°F (121°C) is considered too high for the sensor reporting.
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.
- 1Check the coolant level in the reservoir. If low, fill it and retest. Decision: Is the coolant level normal?
- 2Inspect the wiring and connectors to the coolant temperature sensor for damage or corrosion. Decision: Are the connections secure and undamaged?
- 3Using a scan tool, monitor the coolant temperature reading while the engine is running. Is it reading above 250°F (121°C) when the engine is warm?
- 4If the reading is high, disconnect the sensor and measure the resistance. It should be around 2.5k ohms at 190°F (88°C). Decision: Is the sensor resistance within range?
- 5If the sensor checks out, perform a visual inspection for any leaks or blocked passages in the cooling system.
Common causes
- Faulty coolant temperature sensor
- Shorted wiring to the sensor
- Poor electrical connection at the sensor
- Coolant level too low
- Air in the cooling system causing false readings
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to avoid driving until the issue is fixed, as overheating can cause serious engine damage.
Will this code come back after clearing?
Yes, if the underlying issue isn't fixed, the code will likely return.
Why does this code show up with another fault code?
It may be a sign of a related issue, such as a faulty sensor or cooling system problem.
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