SPN 3251 FMI 0
CAUTION
Particulate filter
The particulate filter is plugged and the engine is losing power.
SPN 3251 FMI 0: The particulate filter is plugged and the engine is losing power. Caution: you can keep driving carefully, but the engine may derate; get it addressed soon.
Mechanical · Aftertreatment / DPF
What it means
DPF differential pressure went above its limit. Soot did not burn off during normal regeneration, usually from short trips, a mis-reading pressure sensor, or plugged pressure hoses. Left alone, the engine will enter a torque and speed derate.
Most likely causes
Soot loading from short trips without a complete regen
Very likely
Differential pressure sensor hoses plugged with soot
Likely
Differential pressure sensor out of calibration
Likely
Ash-loaded DPF at end of service life
Less likely
Tests, cheapest and most decisive first
1. Read DPF differential pressure at idle with the scanner
Expected result: Under 1 kPa at warm idle
Tool: J1939 scanner
2. Inspect the pressure sensor hoses
Expected result: Clean hoses, no soot and no kinks
3. Attempt a full parked regeneration
Expected result: Regen completes and pressure drops
Tool: J1939 scanner
Read it off your own dash
Take one photo and DERATE tells you whether you can keep driving.
DERATEDERATE assists. It does not replace inspection by a qualified technician.