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Fault Code Reference

SPN 3482 FMI 11AftertreatmentInducement Risk

Aftertreatment Diesel Particulate Filter Outlet NOx 1 - Root Cause Not Known

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Overview

Fault Code

SPN 3482 / FMI 11

Category

Aftertreatment

Derate Risk

No

Regen Inhibit

No

Inducement Risk

Yes — SCR inducement possible

Component Location: DPF outlet NOx sensor (sensor 2) is mounted on the aftertreatment system downstream of the DPF and upstream of or at the SCR catalyst outlet, typically on the mid-to-rear undercarriage or frame-mounted aftertreatment assembly.

Common Symptoms

  • Check engine light illuminated
  • Engine derate or reduced power
  • Aftertreatment system fault warnings on dash
  • Poor fuel economy
  • Exhaust aftertreatment malfunction indicator

Root Causes

  • Failed or degraded SCR catalyst reducing NOx conversion efficiency DEF (urea) quality issue — diluted, contaminated, or incorrect concentration Faulty or drifted DPF outlet NOx sensor (sensor 2) providing inaccurate readings DEF dosing system malfunction — clogged or malfunctioning DEF injector DEF supply module pump failure causing insufficient reagent delivery SCR catalyst poisoning from lube oil or fuel sulfur contamination Faulty upstream (inlet) NOx sensor causing incorrect conversion efficiency calculation ACM software or calibration issue misinterpreting NOx sensor data Exhaust system leak upstream of SCR allowing unmetered exhaust bypass Engine running out of specified NOx emission range due to fueling or EGR fault

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Derate Behavior

Power Derate

No

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 3482 FMI 11 (Root Cause Not Known) may inhibit or suspend active DPF regeneration events and can trigger a regen inhibit or derate condition depending on OEM calibration. SCR system derate (torque or speed reduction) may be commanded if NOx conversion efficiency remains out of range. The ACM may prevent regen to avoid further uncontrolled NOx emissions during a fault state.

System Interactions

SPN 3482 FMI 11 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 3482 FMI 11 — 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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