Coolant Temperature - High
Engine coolant temperature is too high or out of 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 thinks the coolant temperature is too high, which can be due to an overheating engine or a faulty sensor reading.
What the computer is actually seeing
The ECM reads a coolant temperature signal that exceeds the normal range, typically over 220°F (104°C) for diesel engines.
What a healthy reading looks like
Coolant temperature should be around 185°F to 210°F (85°C to 99°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 coolant level in the reservoir. If low, top it off and monitor for leaks.
- 22. Inspect the wiring and connector on the coolant temperature sensor for damage or corrosion.
- 33. Ensure the thermostat is not stuck closed by testing its operation (should open around 195°F or 90°C).
- 44. Check for proper operation of the water pump; ensure coolant is circulating through the system.
- 55. Use a scan tool to monitor the live data and compare the coolant temperature sensor reading against the actual temperature of the engine. If the readings do not match, replace the sensor.
Common causes
- Low coolant level
- Failed thermostat
- Worn out water pump
- Bad coolant temperature sensor
- Blocked radiator
Typical repair cost
$$-$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, you risk overheating the engine, which can cause severe damage.
Will this code come back after I clear it?
If the underlying issue isn't fixed, yes, it will likely return.
Why does this code appear along with SPN 110 and SPN 111?
Those codes also relate to engine temperature, indicating a potential theme of overheating or cooling system failure.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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