What is SPN 639 FMI 2 KENWORTH & How to Solve It?

What is SPN 639 FMI 2:

SPN 639 FMI 2 indicates a problem with the Engine Coolant Temperature Sensor in a Kenworth vehicle. FMI 2 suggests that the ECM is receiving an abnormal signal from the sensor, indicating that it’s out of the expected range. This can cause poor engine performance, especially when the coolant temperature is inaccurately monitored.

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Why This Happens:

• Faulty coolant temperature sensor.
  
• Damaged or shorted wiring in the sensor circuit.
  
• Corroded or loose sensor connectors.
  
• Low coolant levels affecting the sensor readings.
  
• ECM misinterpreting the sensor signal.
  
  

How to Fix It:

1. Inspect the coolant temperature sensor for damage or malfunction.
   
2. Test the sensor’s voltage and resistance to verify it’s within specifications.
   
3. Check wiring and connectors for corrosion or damage.
   
4. Replace the faulty sensor if it’s out of specification.
   
5. Ensure the coolant level is correct and the system is functioning properly.
   
   

How to Avoid It Before It Happens:

• Perform regular inspections of the coolant temperature sensor and wiring.
  
• Keep connectors clean and free from corrosion.
  
• Maintain proper coolant levels and replace coolant at recommended intervals.
  
• Use diagnostic tools to monitor sensor performance.
  
• Clue’s Equipment Maintenance services help monitor engine coolant health and prevent temperature sensor-related issues before they affect performance.