Engine Coolant Temperature Sensor 1 Out of Range
The engine coolant temperature sensor is reporting a value outside of its expected range.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine has a sensor that measures the temperature of the coolant to prevent overheating. When it reads too high or low, it means something is wrong with the sensor or engine cooling system.
What the computer is actually seeing
The engine control module (ECM) receives a signal from the coolant temperature sensor, which should normally range between approximately 185°F (85°C) and 220°F (104°C) during normal operation.
What a healthy reading looks like
Normal coolant temperature is expected between 185°F - 220°F. If the reading drops below 140°F (60°C) or goes above 240°F (115°C), this triggers the code.
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 for any visible wiring issues around the coolant temperature sensor, including frays or corrosion. If found, repair as necessary. - Decision: If wiring is okay, move to step 2.
- 2Test the coolant level in the reservoir. Ensure it is at proper operating level. - Decision: If coolant is low, refill and retest. If still an issue, move to step 3.
- 3Measure the resistance of the coolant temperature sensor when the engine is cold. Expect a value near 10,000 ohms. If significantly off, replace the sensor. - Decision: If resistance is normal, move to step 4.
- 4Start the engine and monitor the temperature gauge on the dashboard. Ensure readings align with expected values (185°F - 220°F). If reading is abnormal, check the thermostat and ECM. - Decision: If temperature is erratic and all components seem okay, consider ECM diagnostics.
Common causes
- Faulty coolant temperature sensor
- Wiring issues (frayed, shorted, or corroded)
- Coolant leaks leading to low levels
- Faulty thermostat causing incorrect coolant flow
- ECM programming issue
Typical repair cost
$$-$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to resolve it soon, as overheating could lead to engine damage.
Will this code come back after clearing?
If there's an ongoing issue with the sensor or system, it will likely return.
Why does it sometimes pair with SPN 1508?
SPN 1508 is related to sensor performance, indicating a potential fault in the same system.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →