Engine Coolant Temperature (ECT) Sensor Voltage High
ECT Sensor is reading a voltage that is too high for the expected engine temperature.
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What it means (plain English)
The ECT sensor measures the temperature of the engine coolant. If it senses a voltage higher than what is normal, it indicates the coolant is hotter than expected or there’s a sensor issue.
What the computer is actually seeing
The engine control module (ECM) expects a voltage range from the ECT sensor between 0.5V (around -40°C / -40°F) to 4.5V (about 150°C / 302°F). Anything above 4.5V is considered high and triggers a fault code.
What a healthy reading looks like
Normal ECT voltage ranges from 0.5V to 4.5V, corresponding to temperatures from -40°C to 150°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. Inspect the wiring and connector for the ECT sensor. Look for fraying, shorts to ground, or corrosion.
- 22. With the connector unplugged, measure the ECT sensor resistance. It should typically be between 2.5k ohms (at 20°C) to about 0.3k ohms (at 100°C).
- 33. Reconnect the sensor and use a scan tool to monitor ECT data. Compare the actual voltage reading against the expected values from a reference temperature chart.
- 44. If the voltage is above 4.5V, replace the ECT sensor. If it’s within the range but fluctuates, check the wiring and connectors again. If everything checks out, consider reprogramming or replacing the ECM.
Common causes
- Shorted wiring to the ECT sensor
- Faulty ECT sensor
- Poor connector connection or corrosion
- ECM software issue
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; however, if the engine is running hot, it’s better to address it soon. Driving with overheating issues can damage the engine.
Will this issue come back after repair?
If the root cause is fixed, like replacing the sensor or repairing the wiring, it should not come back.
Why does this code sometimes pair with SPN 262 or SPN 263?
SPN 262 or 263 relate to related temperature or coolant level readings, which can be affected by the same issues causing SPN 271.
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