Engine Coolant Temperature Sensor High
High signal detected from the engine coolant temperature sensor.
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What it means (plain English)
The engine computer is getting a voltage from the coolant temperature sensor that's too high. This usually means the sensor or its wiring is faulty.
What the computer is actually seeing
The engine control module (ECM) expects a voltage signal from the coolant temperature sensor typically between 0.5V (cold) and 4.5V (hot). When it reads over 4.5V, it triggers this fault code.
What a healthy reading looks like
Expected sensor voltage is between 0.5V and 4.5V as temperature varies from cold (around 185°F) to hot (around 212°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. Visually inspect the wiring and connector at the coolant temperature sensor for damage or corrosion. Repair or replace as necessary.
- 22. Check the engine coolant level; ensure it's adequate to prevent overheating. Refilling if necessary.
- 33. Use a multimeter to measure the voltage at the coolant temperature sensor when the engine is at operating temperature. Confirm voltage is between 0.5V and 4.5V.
- 44. If voltage is too high, disconnect the sensor and measure the voltage again with the key on, engine off. If voltage remains high, suspect faulty wiring or ECM. If normal, replace the coolant temperature sensor.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or short circuit in the harness
- Poor connection or corroded connector at the sensor
- Faulty ECM calibration or failure
Typical repair cost
$$
Related codes
Frequently asked questions
Can I still drive my vehicle with this code?
It's drivable but not advisable long-term; overheating can occur if the actual temperature isn't monitored correctly.
What happens if I ignore this code?
The engine may run inefficiently, and you risk engine damage if overheating occurs.
Why does this code come up with low coolant levels?
Low coolant can cause erroneous readings from the sensor, leading to a high voltage signal.
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