What is SPN 5392 FMI 31 & How to Solve It?

What is SPN 5392 FMI 31:

This code signals a general aftertreatment or emissions-related abnormal condition that is undefined but affecting system operation.

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Why This Happens

• Multiple minor emissions-related faults active simultaneously.
• DEF dosing irregularities not assigned to a single fault.
• Sensor values out of sync (NOx, temp, pressure).
• Software delay in aftertreatment control response.
  
  

How to Fix It

1. Scan for additional active or pending emissions-related fault codes.
2. Inspect all sensors in the aftertreatment system.
3. Verify DEF quality, level, and dosing performance.
4. Clear fault codes and monitor system behavior through regen cycle.
   
   

How to Avoid It Before It Happens

1. Regularly test DEF fluid and replace filters.
2. Clean sensors during routine regen maintenance.
3. Leverage Clue’s Preventive Maintenance to schedule regular inspections of the aftertreatment system and ensure proper sensor calibration and DEF quality.