Engine Coolant Temperature (ECT) Sensor
Indicates a problem with the Engine Coolant Temperature sensor value.
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What it means (plain English)
The Engine Coolant Temperature sensor is supposed to measure how hot the coolant is. If it's not reading right, the engine might run too hot or too cold, causing efficiency issues.
What the computer is actually seeing
The engine control module expects a voltage signal from the ECT sensor that varies based on coolant temperature, typically between 0.5V (around -40°C) and 4.5V (around 125°C).
What a healthy reading looks like
When the engine is at operating temperature (around 90-95°C), the ECT sensor should report around 1.5V to 2.5V, implying proper temperature measurements.
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 and top it off if necessary. Low coolant can cause inaccurate readings.
- 22. Inspect the wiring and connector going to the ECT sensor for damage or corrosion. Repair as needed.
- 33. Use a scan tool to read the live data for the ECT sensor. Compare the voltage value against the expected values at different temperatures.
- 44. If the sensor voltage is outside the expected range, replace the ECT sensor and clear the fault code.
- 55. If the fault code returns after replacing the sensor, check the wiring continuity and resistance.
Common causes
- Faulty ECT sensor
- Wiring issues or connectors damaged
- Coolant level low or incorrect
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's manageable but could lead to overheating or poor engine performance, so monitor the temperature gauge closely.
Will this code come back after clearing it?
If the underlying issue isn't fixed (like a bad sensor or wiring), it will likely return.
Why does this code pair with SPN 100?
SPN 100 is often related to the same system, indicating a general issue with the temperature sensor or nearby components.
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