What is SPN 2648 FMI 31 & How to Solve It?

What is SPN 2648 FMI 31:

SPN 2648 relates to the Diesel Particulate Filter (DPF) Differential Pressure, and FMI 31 means the engine has detected an abnormal condition not specifically defined, but likely caused by pressure imbalance in the filter system.

This often means there’s either a buildup of soot or a sensor signal issue that prevents the system from accurately measuring pressure across the DPF — putting regeneration and emissions control at risk.

‍

Why This Happens

• Blocked or excessively loaded DPF.
• Plugged pressure sensor lines.
• Faulty differential pressure sensor.
• Cracked or damaged DPF.
• Leaking exhaust before or after the DPF.

‍

How to Fix It

1. Inspect the DPF for excessive soot or physical damage.
2. Check sensor hoses for clogs or leaks.
3. Replace the DPF differential pressure sensor if readings are off.
4. Run a forced regeneration if filter loading is high.
5. Verify the exhaust system is sealed and pressure readings are consistent.
6. Clear the code and recheck for accuracy.

‍

How to Avoid It Before It Happens

1. Stick to the regen schedule and avoid interrupting active regenerations.
2. Monitor soot load and pressure values weekly.
3. Replace pressure sensor lines before they clog.
4. Use high-quality fuel and avoid extended idling.