Engine Coolant Temperature Sensor Circuit Low
The coolant temperature sensor is reporting a low signal.
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What it means (plain English)
The engine control module (ECM) is seeing a voltage from the coolant temperature sensor that is lower than expected, indicating that the sensor might be faulty or there's an issue with the wiring.
What the computer is actually seeing
The ECM expects the coolant temperature sensor to output a voltage between 0.5V to 4.5V depending on engine temperature. A voltage below 0.2V specifically indicates a problem.
What a healthy reading looks like
Normal coolant temperature approx 190°F should yield about 2.5V to 3.5V from the sensor.
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.
- 1Check the coolant level in the reservoir and radiator, ensure it's at the correct level.
- 2Inspect the wiring and connector for the coolant temperature sensor for any signs of wear, corrosion, or disconnection. Repair or replace as necessary.
- 3Using a multimeter, measure the voltage at the coolant temperature sensor connector. If the voltage is below 0.2V, move to the next step.
- 4Disconnect the coolant temperature sensor and check the resistance of the sensor. At room temperature (about 70°F), you should see a resistance of about 2.5k ohms. If resistance is significantly lower, replace the sensor.
- 5Reconnect the sensor and verify the voltage again. If the issue persists after replacing the sensor, consider testing the ECM.
Common causes
- Faulty coolant temperature sensor
- Wiring or connector issues causing low voltage
- Coolant level too low
- Internal ECM fault
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It is not recommended to drive with this code as it may affect engine performance and could lead to overheating.
Will this code come back after I clear it?
If the underlying issue isn't fixed, the code will likely return.
Why does this code pair with other codes?
Multiple fault codes can indicate related issues, such as a sensor or wiring problem affecting multiple systems.
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