What is SPN 793 FMI 2 & How to Solve It?

What is SPN 793 FMI 2:

SPN 793 FMI 2 refers to an issue with the Crankshaft Position Sensor. FMI 2 indicates that the ECM is receiving an abnormal signal from the crankshaft position sensor, potentially leading to problems with engine timing, stalling, misfires, or difficulty starting the engine.

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Why This Happens:

• Faulty crankshaft position sensor.
  
• Damaged or shorted wiring in the sensor circuit.
  
• Loose or corroded sensor connectors.
  
• ECM misinterpretation of the sensor signal.
  
• Mechanical issues affecting crankshaft position readings.
  
  

How to Fix It:

1. Inspect the crankshaft position sensor for physical damage or malfunction.
   
2. Check wiring and connectors for visible damage or corrosion.
   
3. Test the sensor’s voltage and resistance to ensure it is within specifications.
   
4. Replace the faulty crankshaft position sensor if necessary.
   
5. Ensure the ECM is correctly interpreting the sensor’s data.
   
   

How to Avoid It Before It Happens:

• Regularly inspect the crankshaft position sensor and wiring.
  
• Keep connectors clean and free from corrosion.
  
• Perform routine diagnostic checks on sensor performance.
  
• Verify the ECM’s signal processing for accuracy.
  
• Clue’s Equipment Maintenance services track sensor health and detect issues before they affect engine timing.