Home › Fault codes › SPN 3251 FMI 3
SPN 3251 FMI 3 — DPF differential pressure — voltage high
SeriousAftertreatmentPower derate likely — plan to stop soon
Applies to: Sae
DPF differential pressure — voltage high.
Don't risk it — get a diesel tech on the truck.
Your SPN/FMI rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Signal wire shorted to 5V
- Failed sensor
First moves (roadside)
- Unplug sensor — fault should invert
FAQ
What does SPN 3251 FMI 3 mean?
DPF differential pressure — voltage high.
How serious is SPN 3251 FMI 3?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 3251 FMI 3?
The most common cause is: Signal wire shorted to 5V. Other possibilities include Failed sensor.
Can I keep driving with SPN 3251 FMI 3?
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Throwing this code right now?
Find a mechanic or related guides
General diagnostic guidance for heavy-duty diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack). Not a substitute for a scan-tool diagnosis on your specific truck.