What is SPN 94 FMI 4 & How to Solve It?

What is SPN 94 FMI 4:

SPN 94 FMI 4 refers to a low voltage condition in the Engine Coolant Temperature Sensor Circuit. FMI 4 suggests that the ECM is receiving an unusually low voltage from the coolant temperature sensor, which can lead to improper temperature readings and potentially cause engine overheating or inefficient operation.

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Why This Happens:

• Faulty engine coolant temperature sensor.
  
• Shorted or damaged wiring in the sensor circuit.
  
• Corroded or loose sensor connectors.
  
• Low coolant levels causing inaccurate readings.
  
• ECM failure to interpret the sensor’s data.
  
  

How to Fix It:

1. Inspect the engine coolant temperature sensor for damage or malfunction.
   
2. Test the sensor’s voltage and resistance to ensure proper functioning.
   
3. Check the wiring and connectors for damage, corrosion, or loose connections.
   
4. Replace the faulty sensor if necessary.
   
5. Ensure the coolant system is functioning properly and coolant levels are maintained.
   
   

How to Avoid It Before It Happens:

• Regularly inspect the coolant temperature sensor and wiring.
  
• Keep connectors clean and free from corrosion.
  
• Ensure that coolant levels are correct and that the cooling system is serviced regularly.
  
• Perform diagnostic checks to ensure sensor accuracy.
  
• Clue’s Equipment Maintenance services provide ongoing monitoring of coolant systems to detect sensor issues before they lead to engine problems.