SPN 3251 FMI 4 — DPF differential pressure — voltage low
What it means: DPF differential pressure — voltage low.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Unplug sensor — fault should invert
Don't risk it — look up listed providers near you and give them this SPN/FMI when you call.
Listed providers nearest Phoenix, AZ
Closest first. Tell them SPN 3251 FMI 4 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Phoenix, AZ · (623) 304-4187
- 0.0 mi away — based in Phoenix, AZ · (480) 458-7715
- 0.0 mi away — based in Phoenix, AZ · (480) 530-7347
Applies to: Detroit · Sae
What SPN 3251 FMI 4 means
DPF differential pressure — voltage low.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Signal to ground
- Failed sensor
- Signal short ground
First moves (roadside)
- Unplug sensor — fault should invert
FAQ
DPF differential pressure — voltage low.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Signal to ground. Other possibilities include Failed sensor; Signal short ground.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside SPN 3251 FMI 4, or share the same subsystem.
- Aftertreatment 1 Diesel Particulate Filter Differential Pressure - Data Valid But Above Normal Operating Range, Most Severe Level (DPF severely restricted / plugged) (SPN 3251 FMI 0)
- DPF Differential Pressure — Data Erratic (SPN 3251 FMI 2)
- DPF differential pressure — voltage high (SPN 3251 FMI 3)
- SCR Operator Inducement — Severe Derate Active (SPN 5246 FMI 0)
- Aftertreatment 1 Diesel Exhaust Fluid Quality - Data Valid But Below Normal Operating Range, Most Severe Level (DEF quality/concentration incorrect) (SPN 4364 FMI 1)
- DEF Dosing Unit — Not Responding Properly (SPN 3361 FMI 7)
- SCR Conversion Efficiency — Below Threshold (SPN 4364 FMI 18)
- Diesel Particulate Filter — Soot Accumulation (P2463)
Same symptom: Regen problems
Other codes that block a regen or come back as soot load climbing.
- DPF Soot Accumulation Restriction (P2460) · Aftertreatment & Emissions
- DPF inlet temp sensor — voltage high (SPN 3241 FMI 3) · Aftertreatment & Emissions
- DPF outlet temp erratic (SPN 3242 FMI 2) · Aftertreatment & Emissions
- DPF outlet temp sensor — voltage high (SPN 3246 FMI 3) · Aftertreatment & Emissions
- DPF soot load high — warning (SPN 3719 FMI 15) · Aftertreatment & Emissions
- DPF ash load very high — service required (SPN 3720 FMI 0) · Aftertreatment & Emissions
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.