Engine Coolant Temperature Sensor High
ECU detects a high signal from the engine coolant temperature sensor.
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What it means (plain English)
The engine coolant temperature sensor is sending a high voltage signal, indicating that the engine is running hotter than normal or the sensor is faulty.
What the computer is actually seeing
The Engine Control Unit (ECU) sees a voltage higher than 5 volts from the coolant temperature sensor signal line, indicating an over-temperature situation.
What a healthy reading looks like
Coolant temperature should range between 85°C to 100°C, with a corresponding voltage of around 0.5V to 4.5V depending on temperature state.
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. Is it low? If yes, top up and retest. If normal, proceed to step 2.
- 22. Inspect the wiring and connectors at the coolant temperature sensor for damage or corrosion. Are the connectors secure and free of corrosion? If no, repair or replace as necessary and retest.
- 33. Use a multimeter to measure the voltage at the coolant temperature sensor while the engine is at operating temperature. Is this voltage between 0.5V and 4.5V? If yes, the sensor is likely good. If it’s above 5V, replace the sensor.
- 44. If the sensor is replaced and the code returns, check for any short circuits between the signal wire and the power supply. Is a short detected? If yes, repair the wiring.
- 55. If all checks are passed with the new sensor and no shorts found, check the engine for overheating conditions or cooling system functionality.
Common causes
- Wiring issue or short circuit to power
- Faulty engine coolant temperature sensor
- Overheating engine due to low coolant or other cooling issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not safe to drive if the engine is actually overheating; constant monitoring of the temperature gauge is essential until fixed.
Will this code come back after repairs?
If repairs are done correctly and no underlying issues exist, it should not return.
Why does this code sometimes pair with SPN 100?
SPN 100 indicates a general engine temperature issue; both codes can show up if the cooling system is failing.
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