SPN 3719 FMI 3AftertreatmentMedium
DPF Soot Load Sensor - Voltage High
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 3719 / FMI 3
Category
Aftertreatment
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: The DPF soot load sensor is typically mounted on or integrated into the diesel particulate filter housing in the exhaust system.
Common Symptoms
- Check engine light illuminated. MIL lamp on. Possible yellow engine warning lamp. Inaccurate soot load readings on scan tool (may show 0% or fixed high value). DPF regeneration may not initiate properly or may run longer than normal. Possible increase in fuel consumption if system defaults to timed regens. No noticeable drivability issues in most cases.
Root Causes
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
This fault typically inhibits automatic active regeneration because the ACM cannot accurately determine DPF soot loading. System may default to timed regeneration intervals or require parked/stationary regen to be commanded manually via scan tool. In some cases, the system will use exhaust backpressure sensor as a backup to estimate soot load, but regen efficiency may be reduced. Technician-forced regen should still be possible for diagnostic purposes.
System Interactions
SPN 3719 FMI 3 interacts with the following systems and may trigger cascading faults if not resolved promptly.
DPF differential pressure monitoring — soot load calculations affected
SCR NOx conversion efficiency — DEF dosing strategy may be altered
Active regen inhibit logic — regen may be blocked or delayed
Engine protection derate — ECM may reduce power to protect components
TSB Reference: No confirmed TSBs — verify in OEM service portal. Some OEMs have released service bulletins for soot sensor harness routing and connector sealing issues. Cummins, Detroit Diesel, and Paccar have had field service campaigns related to aftertreatment sensor wiring — check OEM QuickServe, DTNA ServiceConnect, or Paccar Information System for model-specific bulletins.
Common Diagnostic Mistakes
Replacing the sensor without verifying wiring continuity and supply voltage first.
Clearing codes without identifying and resolving the root cause — the fault will return.
Ignoring related active faults — cascading faults often share a root cause.
Skipping the connector inspection — corrosion and damaged pins are a leading cause of sensor faults.
Condemning the ECM before exhausting all wiring and component tests.
Replacing the DPF without verifying the regen system is functional — a failed regen injector will reload the new DPF.
Ignoring DEF quality — contaminated DEF causes SCR efficiency faults that look like hardware failures.
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 3719 FMI 3 — Full FSM Sequence & Repair Steps — includes wiring notes, sensor specs, and gated repair procedures.
Authority References
Diagnostic procedures on this page are informed by OEM service literature and industry standards.
EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx standards.Cummins QuickServe OnlineOfficial Cummins service manuals, fault code lookup, and TSB database.Detroit Diesel DiagnoCentralDetroit Diesel diagnostic procedures, DDDL documentation, and service literature.PACCAR MX Engine ServicePACCAR MX-11 and MX-13 engine service documentation and DAVIE diagnostic guides.Volvo/Mack Tech ToolVolvo and Mack engine fault code reference and PTT/Tech Tool diagnostic procedures.ASE — Diesel Truck Technician CertificationNational Institute for Automotive Service Excellence — T2 Diesel Engines certification standards.
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