Engine Coolant Temperature (ECT) Sensor Circuit High
The engine coolant temperature sensor reading is too high.
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What it means (plain English)
The ECT sensor measures the temperature of the coolant, and if it sees a high reading (like over 240°F), it triggers this code, indicating something might be wrong with the sensor or the cooling system.
What the computer is actually seeing
The PCM expects the ECT to send a signal that corresponds to coolant temperatures, generally between 180°F and 220°F (82°C - 104°C). If it sees a voltage reading above 4.5V or below 0.5V, it triggers this code.
What a healthy reading looks like
Expected ECT voltage should range from 0.5V to 4.5V corresponding to 180°F to 240°F. A valid reading should not exceed 240°F (or around 4.5V).
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. If it's low, top it off and recheck for the code.
- 22. Inspect the wiring and connector for the ECT sensor. Look for damage, corrosion, or loose connections.
- 33. Use a scan tool to read the ECT value. It should be within expected range (ideally 180°F - 220°F). If it's showing much higher (over 240°F) or very low, proceed to the next step.
- 44. Measure the voltage at the ECT sensor connection when the engine is at operating temperature. It should be between 0.5V and 4.5V. If not, replace the sensor.
- 55. If the ECT sensor is good, verify the power and ground circuits to the sensor. Repair as necessary.
- 66. Replace the thermostat if the engine is overheating or not reaching operating temperature.
Common causes
- Faulty ECT sensor
- Shorted wiring to ECT
- Open circuit in ECT wiring
- Thermostat stuck closed causing overheating
- Incorrect coolant type
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity indicates potential drivability issues; it's best to fix soon.
Will the code come back if I just clear it?
It's likely to return if the underlying issue isn't resolved.
Why is this paired with SPN 0388 or other codes?
Similar systems function together, so faults in one can affect the others.
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