Engine Coolant Temperature Sensor 1
Engine coolant temperature sensor signal high fault.
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What it means (plain English)
The engine coolant temperature sensor is reading a high voltage, indicating the engine might be overheating or the sensor is faulty.
What the computer is actually seeing
The engine control module (ECM) sees a voltage above the normal operating range, usually above 4.5V which suggests a problem with the sensor or wiring.
What a healthy reading looks like
Normal operating voltage should be between 0.5V to 4.5V depending on temperature; 0.5V around -40°C and 4.5V around 125°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 engine coolant temperature sensor wiring and connectors for damage or corrosion. If found, repair/replace the damaged components. Check for codes again.
- 22. Measure the voltage at the coolant temperature sensor connector with the key on (engine off). Expected should be around 0.5V to 4.5V. A voltage significantly higher than 4.5V indicates a short. If so, locate and repair the short to power in wiring.
- 33. If voltage is normal, use a scan tool to compare the reading from the coolant temperature sensor with the actual engine temperature. If they do not match, replace the coolant temperature sensor.
- 44. After replacing the sensor, clear the codes and start the engine to verify normal operation and the absence of the code.
Common causes
- Faulty engine coolant temperature sensor
- Wiring damage or short to power
- Corrosion in connectors
- Coolant leaks affecting sensor operation
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive with this code active?
It's not recommended to drive with this code; overheating can damage your engine.
Will this code come back after repairs?
If the underlying issue is resolved, the code should not return.
Why does this code appear with low coolant levels?
Low coolant can cause irregular temperature readings, triggering this fault.
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