Detailed guide for SPN 520372 FMI 31
Back to top ↑This is the “regen wants to happen but can’t” code.\n\nMost common root cause is low exhaust temperature from short trips and idling, especially in winter.
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Share ↓SPN 520372 FMI 31Severity: Warning
SPN 520372 FMI 31: Aftertreatment regen inhibited – operating conditions not met
Quick Answer
Aftertreatment regen inhibited – operating conditions not met
Code
SPN 520372 FMI 31
Severity
Warning
Applies to
Check OEM application
Can I drive?
Driving suitability is not established by this code alone.
Common Symptoms
- Regen will not start
- Frequent regen messages
- DPF soot load rises
Likely Causes
- Low speed/low load driving
- Cold weather exhaust temps too low
- Inhibit switch or PTO logic active on some setups
Common Fixes
- Drive at steady highway speed to raise temps
- Confirm inhibit is OFF if equipped
- Fix temp sensor faults that prevent regen
Full technical sections↓
What does SPN 520372 FMI 31 mean?
Back to top ↑Aftertreatment regen inhibited – operating conditions not met
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