Engine Coolant Temperature Sensor - High
The engine coolant temperature sensor is reading too high.
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What it means (plain English)
The engine's computer thinks the coolant is too hot, which could lead to overheating, and it’s taking measures to protect the engine.
What the computer is actually seeing
The Engine Control Module (ECM) sees a coolant temperature reading above the set threshold, typically above 240°F (116°C), which triggers the fault code.
What a healthy reading looks like
Expected coolant temperature sensor readings should be between 180°F (82°C) and 220°F (104°C) during regular operation.
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 it's low, add coolant and see if the code clears. Decision: If the code returns, proceed to step 2. If it doesn't, monitor for future issues.
- 22. Inspect the wiring and connections to the engine coolant temperature sensor for damage or corrosion. Repair or clean as necessary. Decision: If wiring looks good and code returns, proceed to step 3. If repaired and code clears, keep monitoring.
- 33. Using a scan tool, compare the temperature reading from the sensor to the actual temperature of the coolant with an infrared thermometer. Decision: If the sensor reading is consistently higher than the actual temperature, replace the coolant temperature sensor. If reading is accurate, proceed to step 4.
- 44. Check the thermostat operation by monitoring engine temperature as it warms up. If the engine overheats rapidly, the thermostat may be stuck closed. Decision: If the thermostat is faulty, replace it and check for proper operation.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues or short circuits in the sensor circuit
- Low coolant level or air pockets in the cooling system
- Faulty thermostat stuck in the closed position
- Cooling fan not operating properly
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, driving with a high coolant temperature reading can lead to engine overheating and severe damage.
Will this code come back after clearing?
If the underlying issue isn't fixed, such as a faulty sensor or thermostat, the code will likely return.
Why does this code appear with other codes like SPN 100?
Other codes related to engine temperature or performance may show up due to the engine's protective measures against overheating.
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