Coolant Temperature Sensor 1 High
Engine coolant temperature sensor signal is too high.
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What it means (plain English)
The computer thinks the coolant temperature is higher than normal, which might not be true. It can cause poor engine performance or damage unless fixed.
What the computer is actually seeing
The engine control module (ECM) sees a voltage from the coolant temperature sensor that is above the expected range, typically over 5 volts.
What a healthy reading looks like
Coolant temperature sensor readings should be between 0.5 to 4.5 volts, corresponding to temperature ranges of -40 to 200 °C (-40 to 392 °F).
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 coolant level; ensure it's at the proper level.
- 2Inspect the coolant temperature sensor wiring for damage or loose connectors. Repair as necessary.
- 3Test the coolant temperature sensor for proper resistance values at varying temperatures.
- 4Check voltage at the sensor connector; should be between 0.5 - 4.5 volts. If voltage is too high, replace the sensor.
- 5Clear the code and test drive the vehicle. If the code comes back, consider checking the ECM.
Common causes
- Faulty coolant temperature sensor
- Damaged wiring or connectors
- Coolant leaks or low coolant level
- Issues with ECM (rare)
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally safe to drive, but you may experience poor engine performance or overheating.
Will the code come back?
If the underlying issue isn't fixed, the code will likely return after clearing.
Why does this code pair with other codes?
Codes can relate due to shared circuits, like the temperature sensor affecting other systems.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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