What is SPN 1231 FMI 9
- SPN 1231: Refers to a fault related to the engine coolant temperature sensor, indicating that the sensor is providing invalid or out-of-range data regarding the coolant temperature.
- FMI 9: Indicates that the signal from the coolant temperature sensor is out of range or invalid, meaning the ECM is unable to process the data properly.
Together, SPN 1231 FMI 9 signals a malfunction in the engine coolant temperature sensor, which could lead to inaccurate coolant temperature readings, potentially affecting the engine’s cooling system and performance.
Why It Happened
This fault is typically caused by:
- Low coolant levels or coolant leaks.
- A malfunctioning or failed engine coolant temperature sensor.
- Wiring issues between the sensor and ECM, such as loose or damaged connections.
- A faulty thermostat that isn’t regulating coolant temperature properly.
- Contamination in the coolant, which can affect sensor readings.
How to Resolve It
To resolve SPN 1231 FMI 9:
- Check the coolant level and top it off if necessary.
- Inspect the engine coolant temperature sensor for faults, and replace it if necessary.
- Test the thermostat to ensure it is working properly.
- Inspect wiring and connections for damage or corrosion.
- After repairs, clear the fault code and restart the engine to confirm the fix.
How to Avoid Before It Happens
To prevent SPN 1231 FMI 9:
- Regularly check coolant levels and inspect for leaks in the cooling system.
- Perform routine maintenance on the coolant temperature sensor and wiring.
- Use Clue to monitor engine temperature data and receive early alerts for sensor or cooling system failures.
