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Fault Code Reference

SPN 3719 FMI 14AftertreatmentInducement Risk

Aftertreatment 1 DEF Doser 1 - Special Instructions

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Overview

Fault Code

SPN 3719 / FMI 14

Category

Aftertreatment

Derate Risk

Yes

Regen Inhibit

No

Inducement Risk

Yes — SCR inducement possible

Component Location: DEF doser valve is mounted on the DEF decomposition tube or SCR inlet pipe, typically mid-chassis on the exhaust aftertreatment system beneath or alongside the vehicle frame.

Common Symptoms

  • DEF system warning light illuminated
  • Engine derate or power reduction
  • DEF dosing system malfunction message
  • Increased NOx emissions detected
  • DEF consumption appears abnormal

Root Causes

  • DEF doser valve clogged or crystallized with urea deposits requiring cleaning or replacement DEF doser valve stuck open or closed due to internal failure DEF supply line blockage or restriction upstream of doser DEF quality issue causing crystallization within doser assembly DEF doser tip overheating due to insufficient DEF flow for cooling ACM/ECM commanded special service procedure required (doser purge or replacement routine) Wiring harness chafing or connector corrosion at DEF doser connector DEF pump delivery pressure out of specification causing improper atomization Failed or degraded DEF doser solenoid

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Derate Behavior

Power Derate

Yes

SCR Inducement Risk

If left unresolved, this fault may trigger SCR inducement — a progressive derate enforced by the ECM to ensure emissions compliance.

Mileage / Regen Notes

SPN 3719 FMI 14 may inhibit active DPF regeneration if the DEF doser is non-functional, as the SCR system cannot properly dose reductant. Depending on ACM strategy, the system may also inhibit or abort regen to protect the SCR catalyst from undosed exhaust. Derates and regen lockout are possible if the fault is persistent.

System Interactions

SPN 3719 FMI 14 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

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.

Deep-dive diagnostic page: SPN 3719 FMI 14 — 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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