Engine Coolant Temperature Sensor Circuit Low
Indicates the engine coolant temperature sensor signal is below the expected range.
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What it means (plain English)
The engine coolant temperature sensor measures how hot the coolant is. If the reading is too low, it means the sensor might be faulty or there’s an issue with the wiring, allowing cooler temperatures to show when the engine is warm.
What the computer is actually seeing
The engine control module expects the coolant temperature to be between 180°F and 220°F (82°C to 104°C) while the engine is running. If it detects a signal below 140°F (60°C) for an extended period when the engine is warm, it triggers this code.
What a healthy reading looks like
Expected coolant temperature should be between 180°F and 220°F (82°C to 104°C), and the voltage from the sensor should typically be 0.5V to 4.5V depending on 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.
- 11. Inspect the wiring and connectors for the coolant temperature sensor. Look for damaged insulation or loose connections. If okay, proceed to step 2.
- 22. Check the coolant level in the reservoir. It should be at the recommended level. If it's low, add coolant, clear the code, and see if it returns. If it does, go to step 3.
- 33. Measure voltage at the coolant temperature sensor connector with the engine running. You should see a voltage between 0.5V and 4.5V. If not, suspect wiring issues or ECM failure. If voltage is good, go to step 4.
- 44. Replace the coolant temperature sensor and clear the code. Test drive the vehicle to confirm if the code returns.
Common causes
- Faulty coolant temperature sensor
- Open or shorted wiring in the sensor circuit
- Poor connection at the sensor or ECM
- Low coolant level
- Faulty engine thermostat
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity means you can drive it, but it's best to fix it soon to avoid overheating issues.
Will this code come back after clearing?
Yes, if the underlying issue isn't fixed, like a faulty sensor or wiring problem, it will likely return.
Why do I see this code along with SPN 826?
SPN 826 indicates high temperature readings, whereas SPN 827 shows low readings; both relate to the coolant temperature sensor activity.
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