Engine Coolant Temperature
Engine coolant temperature is out of range.
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What it means (plain English)
The engine's computer is telling you that the coolant temperature is either too high or too low, indicating a potential overheating issue or a faulty temperature sensor.
What the computer is actually seeing
The engine control module (ECM) expects the coolant temperature to be between 185°F and 220°F during normal operation. If it falls below 160°F or exceeds 240°F, it triggers this code.
What a healthy reading looks like
Coolant temperature should read between 185°F (85°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 coolant level in the reservoir. If low, top off and retest—if code returns, continue.
- 22. Inspect the wiring and connectors at the coolant temperature sensor for damage or corrosion—repair as needed; if good, continue.
- 33. Use a scan tool to read the actual coolant temperature; compare with gauge reading. If the readings are off, replace the temperature sensor.
- 44. Check the thermostat operation by feeling the upper radiator hose; it should reach temperature (about 185°F) after engine warms—if not, replace the thermostat.
- 55. If all tests pass, consider checking for external coolant leaks that could indicate an overheating issue.
Common causes
- Faulty coolant temperature sensor
- Coolant leaks
- Thermostat stuck open or closed
- Wiring or connector issues to the sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code present?
Moderate severity means you should drive with caution. Overheating can cause engine damage, so check coolant levels and monitor temperature closely.
Will this code come back after resetting?
If the underlying issue isn't fixed, yes, the code will usually reappear.
Why does this code sometimes pair with SPN 410?
SPN 410 deals with the intake air temperature sensor. Together, they can indicate problems with engine cooling or airflow issues.
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