Faulty Engine Coolant Temperature Sensor
The engine coolant temperature sensor is reporting out-of-range values.
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What it means (plain English)
The engine coolant temperature sensor tells the computer how hot the engine coolant is. If it sees a temperature that's way too high or too low, it gets confused and throws a code.
What the computer is actually seeing
The ECM detects the coolant temperature sensor signal outside its expected range, usually below -40°F (-40°C) or above 257°F (125°C).
What a healthy reading looks like
Coolant temperatures should typically be between 180°F (82°C) and 220°F (104°C) when the engine is at normal operating temperatures.
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.
- 1Inspect the coolant temperature sensor wiring and connector for damage or corrosion. Repair or replace as necessary.
- 2Check the engine coolant level; ensure it is between the min and max marks.
- 3Measure the resistance of the coolant temperature sensor: at 68°F (20°C) it should show approximately 2.5 to 3.5 kΩ. If it's out of this range, replace it.
- 4With the engine running, verify the coolant temperature reading on the scan tool. It should match engine temperature, typically between 180°F and 220°F. If not, replace the sensor.
Common causes
- Open or shorted wiring to the coolant temperature sensor
- Failed coolant temperature sensor
- Faulty engine coolant
- Loose connections or corrosion at the sensor connector
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's generally safe to drive but the engine may not perform optimally, and emissions can be affected.
Will this code come back after clearing?
If the underlying issue isn't fixed, expect the code to return shortly after clearing.
Why does this code sometimes pair with other codes?
Related codes often indicate issues with the same system or components, like wiring or coolant sensor faults.
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