Engine Coolant Temperature
Indicates the engine coolant temperature is out of range.
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What it means (plain English)
The engine has a temperature sensor that measures how hot the coolant is, which affects performance. If it's reading too high or too low, something's wrong.
What the computer is actually seeing
The ECM expects the coolant temperature to be between 180°F to 220°F (82°C to 104°C) during normal operation. When it reads below 160°F (71°C) or above 235°F (113°C), it triggers this code.
What a healthy reading looks like
Coolant temperature should normally be between 180°F and 220°F (82°C - 104°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. Check coolant level - should be at the proper fill level. If low, top up and retest; if not low, proceed to the next step.
- 22. Inspect the engine coolant temperature sensor connector and wiring for damage or corrosion; repair if necessary, then retest.
- 33. Using a scan tool, monitor the coolant temperature reading while the engine is running. Verify it corresponds to the actual coolant temperature; if it does not, replace the sensor.
- 44. Test the sensor with an ohmmeter to ensure proper resistance values at various temperatures. Consult service manual for specifics; if faulty, replace the sensor.
- 55. If all components check out and the code returns, investigate the thermostat operation as a last resort; verify if it's opening at the correct temperature.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues in the sensor circuit
- Low coolant level
- Thermostat stuck open or closed
- Coolant contamination
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's usually safe for short distances, but you should fix it soon as it affects engine performance.
Will this code come back after clearing?
It can return if the underlying issue isn’t resolved; monitor it after repairs.
Why does this code pair with high coolant temperature codes?
A fault in the coolant temperature sensor can lead to incorrect readings, causing high temperature alerts.
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