Engine Coolant Temperature Sensor 1
Coolant temperature sensor is out of the expected range.
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What it means (plain English)
The engine coolant temperature sensor measures how hot the coolant is. When it reads too high or too low, the engine thinks there's an overheating issue or that the engine isn't warming up properly.
What the computer is actually seeing
The engine control module (ECM) monitors the coolant temperature sensor's voltage, expecting a range of about 0.5V to 4.5V depending on the actual coolant temperature.
What a healthy reading looks like
At operating temperature, the expected voltage from the coolant temperature sensor should be around 2.5V to 3.0V, corresponding to approximately 190°F to 210°F (88°C to 99°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 in the reservoir; it should be within the specified range. If low, top off and check for leaks.
- 22. Inspect the wiring and connectors at the coolant temperature sensor for damage or corrosion. Repair as necessary.
- 33. Using a scan tool, monitor the coolant temperature sensor readings while the engine is running. Compare the actual temperature with the sensor readings.
- 44. If the sensor readings are outside of 0.5V to 4.5V or not aligning with the actual temp, replace the coolant temperature sensor.
- 55. If replacing the sensor does not resolve the issue, check for shorts in wiring or poor connections. Run continuity tests to ensure proper signal transmission.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or short circuits
- Poor connector connections
- Low coolant level
- Faulty engine thermostat
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's better to fix this soon since it can affect engine performance and fuel economy.
Will this code come back after I clear it?
It may return if the underlying issue isn't resolved, such as a wiring problem or a faulty sensor.
Why does this code sometimes pair with SPN 190?
SPN 190 often shows up with this code because it relates to the coolant temperature sensor circuit, indicating similar issues.
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