Detailed guide for SPN 5397 FMI 31
Back to top ↑What SPN 5397 FMI 31 means
SPN 5397 FMI 31 is documented by Navistar for DPF regenerations occurring too frequently.
The published diagnostic applies to EPA 2014 N9 and N10 SCR engines.
What you may notice
The truck may perform regenerations much more often than normal.
The malfunction indicator lamp or aftertreatment warning can illuminate after repeated detection of the condition.
Frequent regeneration can also increase fuel consumption.
What to check first
Check for other active engine or aftertreatment fault codes and diagnose those first when appropriate.
Inspect the DPF differential pressure sensor connectors and pressure tubes.
Check the exhaust system for leaks, restrictions, damage or soot traces, including areas upstream of the DPF.
Why frequent regeneration happens
Frequent regeneration is usually a symptom rather than the root problem.
The engine may actually be producing excessive soot, or faulty pressure/temperature information may make the controller believe regeneration is required more often than it really is.
Important
This exact diagnostic description is documented for specific Navistar N9/N10 applications. Other manufacturers may use SPN 5397 differently, so confirm the engine family before applying the repair path.
Mechanic community notes for SPN 5397 FMI 31
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