Engine Coolant Temperature (ECT) Sensor Voltage High
Indicates a high voltage from the engine coolant temperature sensor.
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What it means (plain English)
The Engine Control Module (ECM) is getting a voltage reading from the coolant temperature sensor that is higher than expected, usually over 4.7 volts, when it should be between 0.5 and 4.5 volts, indicating a possible sensor or wiring issue.
What the computer is actually seeing
The computer expects the ECT sensor to send a voltage signal based on the coolant temperature. When the temperature is low (around 20°C/68°F), the voltage should be around 0.5 volts. At operating temperature (approximately 90°C/194°F), it should be around 2.5 volts. If it reads above 4.7 volts, it triggers this fault code.
What a healthy reading looks like
0.5 to 4.5 volts depending on coolant temperature; should never exceed 4.7 volts for standard 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. Start by visually inspecting the wiring and connector to the ECT sensor for damage or corrosion. If anything looks off, repair or replace as needed. Decision: Good wiring? Go to Step 2. Bad wiring? Fix it.
- 22. Use a multimeter to measure the voltage at the ECT sensor connector with the engine at operating temperature. Expected voltage should be around 2.5 volts. Decision: Voltage too high? Go to Step 3. Voltage okay? Replace the ECT sensor.
- 33. Check the pink wire for a short to power supply by disconnecting the sensor and measuring voltage at the connector. Decision: Voltage present? Replace the ECT sensor. No voltage present? Inspect the ECM wiring.
Common causes
- Faulty engine coolant temperature sensor
- Shorted wiring to the ECT sensor
- Open circuit or high resistance in sensor circuit
- Bad ground connection for the sensor
Typical repair cost
$$ - $$$ (sensor replacement plus potential wiring repair)
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix it soon, as high coolant temps can lead to overheating, but you may still be able to drive short distances.
Will this code come back after clearing?
If the underlying issue isn't resolved, yes, the code will likely return.
Why does this pair with high idle issues?
An incorrectly reading ECT can cause the ECM to think the engine is colder than it is, keeping the idle higher than normal.
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