Engine Coolant Temperature Sensor Circuit High
Coolant temperature sensor signal is too high.
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What it means (plain English)
The engine control module (ECM) thinks the coolant is way too hot because the temperature sensor is sending a voltage that's too high, over 4.5V, even when the coolant is not that hot.
What the computer is actually seeing
The ECM expects a coolant temperature signal between 0.5V (about 32°F) and 4.5V (about 277°F). Anything above 4.5V indicates a malfunction.
What a healthy reading looks like
Normal coolant temperature readings should be between 0.5V (32°F) and 4.5V (277°F).
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 in the reservoir and radiator. Ensure it's at the correct level. Decision: If low, top off and retest. If okay, proceed to the next step.
- 22. Inspect the coolant temperature sensor wiring and connectors for damage or corrosion. Decision: If any issues found, repair or replace the wiring and retest. If okay, proceed to the next step.
- 33. Use a multimeter to measure the voltage at the coolant temperature sensor connector. Decision: If the voltage is above 4.5V with the engine off, replace the coolant temperature sensor. If under 4.5V, proceed to the next step.
- 44. Check for any ECM fault codes related to the engine cooling system. Decision: If other codes are found, address those issues. If not, replace the engine control module if sensor checks pass.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or short circuits in the sensor circuit
- Corroded or loose connectors
- Engine overheating
- Faulty ECM
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix this soon; the engine could overheat if the sensor is malfunctioning.
Will this code come back if I clear it?
If the underlying issue isn't fixed, yes, the code will return.
Why does this code pair with SPN 220?
SPN 220 indicates the engine temperature exceeds the limit, which can happen if the coolant temp sensor is malfunctioning.
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