Engine Coolant Temperature Sensor 1
Engine coolant temperature is out of range.
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What it means (plain English)
The engine control unit (ECU) is getting readings from the coolant temperature sensor that are too high or too low, indicating a possible issue with the sensor or coolant system.
What the computer is actually seeing
The ECU expects coolant temperature readings between 180°F to 220°F (82°C to 104°C) during normal operation. It detects a sensor input that is either much higher or much lower than these expected values, which triggers the fault code.
What a healthy reading looks like
Normal operating temperature should be between 180°F (82°C) and 220°F (104°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 the engine coolant level. Ensure it's at the correct level and top up if low. Decision: If low, refill and retest. If normal, proceed to next step.
- 22. Inspect the wiring and connector at the coolant temperature sensor for damage, corrosion, or loose connections. Decision: If damaged, repair or replace wiring. If intact, proceed to next step.
- 33. Use a scan tool to monitor the coolant temperature reading during a warm-up cycle. Decision: If reading is within expected range (180°F - 220°F), the issue might be intermittent. If not, proceed to next step.
- 44. Test the coolant temperature sensor with a multimeter. At known temperatures (freeze point, boiling point), check resistance. Decision: If resistance values match expected specs, replace the sensor. If they are off, replace the sensor.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or damaged connectors
- Coolant level low or overheating condition
- Corroded terminals or poor electrical connections
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, it is usually safe to drive, but you should check the coolant level and monitor engine temperature closely.
Will this code come back after clearing it?
It can return if the underlying issue isn't fixed, like a faulty sensor or wiring problem.
Why does this code sometimes pair with SPN 1805?
Both codes relate to temperature measurement issues, indicating problems with coolant temperature sensing components.
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