Coolant Temperature Sensor 1 - Circuit High
The coolant temperature sensor signal is too high or out of expected range.
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What it means (plain English)
The coolant temperature sensor measures how hot the engine coolant is. If the signal is too high, the engine computer thinks the engine is overheating or the sensor is faulty.
What the computer is actually seeing
The engine control module (ECM) sees the coolant temperature signal reading above the normal range, typically over 150°C (302°F), which indicates a problem.
What a healthy reading looks like
Expected coolant temperature should be between 70°C (158°F) and 105°C (221°F) when the engine is at operating temperature.
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; top off if low and retest.
- 2Inspect the coolant temperature sensor wiring for shorts, breaks, or corrosion. Repair as necessary, then retest.
- 3Use a multimeter to check the coolant temperature sensor voltage output; it should be within 0.5V to 4.5V depending on the temperature. If out of range, replace the sensor.
- 4Clear the fault code and start the engine. Monitor the coolant temperature gauge and the OBD-II live data to see if the code returns. If it does, replace the sensor.
Common causes
- Faulty coolant temperature sensor
- Wiring issues like short to power
- Poor connections at the sensor
- Thermostat stuck closed, causing overheating
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best not to drive if the engine is indicating overheating. Address the issue promptly.
Will this code come back?
If the underlying issue isn't fixed, such as a bad sensor or wiring problem, the code will likely return.
Why does this code appear with other codes?
Multiple codes can indicate related issues, like overheating caused by a faulty sensor or thermostat.
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