Coolant Temperature Sensor 1 Out of Range
The coolant temperature sensor is reporting a value outside the acceptable range.
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What it means (plain English)
The engine's computer relies on a sensor to monitor the coolant temperature, which is crucial for optimal engine performance. If this sensor sends a reading that’s too high or too low, the engine management system can’t effectively control fuel injection, meaning it could run inefficiently or even overheat.
What the computer is actually seeing
The engine control module (ECM) expects the coolant temperature should generally be between 160°F to 220°F (70°C to 105°C). If the input from the coolant temperature sensor goes above 240°F (116°C) or below 140°F (60°C), it triggers this fault code.
What a healthy reading looks like
Normal coolant temperature readings should be between 160°F to 220°F (70°C to 105°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 coolant level. If low, top off and recheck if the code returns.
- 22. Inspect wiring and connectors for any visible damage or corrosion. Repair as necessary.
- 33. Use a scan tool to read the coolant temperature. Ensure it's within the range of 160°F to 220°F (70°C to 105°C). If not, proceed to the next step.
- 44. Test the coolant temperature sensor with a multimeter. At normal operating temperature, it should show a resistance between 2.5kΩ to 10kΩ. If not, replace the sensor.
- 55. If the sensor is okay, check the ECM for faults or consider reprogramming if applicable.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or poor connections
- Coolant leaks or low coolant level
- Faulty engine control module (ECM)
- Corroded connectors
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderately safe, but you risk overheating or poor performance—fix soon.
Will this code come back after clearing?
If the underlying issue isn't fixed, it'll likely reappear.
Why might this pair with SPN 1704?
Both codes deal with coolant temperature; if the sensor fails, both might trigger.
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