AI Diesel Tech

Fault Code Reference

SPN 5829 FMI 31AftertreatmentInducement Risk

Aftertreatment 1 Diesel Particulate Filter Condition - Condition Exists

Run Full DiagnosisView Related FaultsSee OEM System Guide

Scan Tool — in guided session

DVOM Testing — in guided session

Connector Pinout — in guided session

DieselVision™ Upload photos — DieselVision™ reads diagrams, connectors, and screens with precision.

Overview

Fault Code

SPN 5829 / FMI 31

Category

Aftertreatment

Derate Risk

Yes

Regen Inhibit

No

Inducement Risk

Yes — SCR inducement possible

Component Location: DPF is located in the exhaust aftertreatment system, typically mounted under or alongside the vehicle frame behind the DOC, with delta pressure and temperature sensors on the DPF canister.

Common Symptoms

  • Check engine light illuminated
  • DPF regeneration required lamp active
  • Frequent active regeneration requests
  • Elevated exhaust backpressure
  • Reduced fuel economy
  • Poor engine performance at higher loads
  • High DPF soot load displayed

Root Causes

  • Excessive DPF soot or ash loading beyond regeneration capability
  • Failed or incomplete active/passive regeneration cycles
  • DPF delta pressure sensor malfunction giving false load readings
  • Blocked or kinked DPF differential pressure sensor lines
  • Faulty DPF temperature sensors causing regen inhibit
  • Extended idle operation leading to soot accumulation
  • Failed diesel oxidation catalyst (DOC) reducing regen efficiency
  • Low exhaust temperatures due to light-duty or short-trip operation
  • DEF/SCR system faults inhibiting regen permission
  • EGR system malfunction causing excessive soot production

Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.

AI walks you through every test — one step at a time. Plans start at $12.95/mo.

Start Guided DiagnosisSee How It Works

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 5829 FMI 31 directly indicates DPF condition exists (overloaded or unable to regenerate). Active and passive regen may be inhibited or failing. Parked regen may be forced via diagnostic tool if no other inhibit conditions are active. Continued operation without resolving the fault risks DPF damage and may result in derate or engine shutdown.

System Interactions

SPN 5829 FMI 31 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 5829 FMI 31 — 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.

Get weekly diesel diagnostic tips

Real-world fault code walkthroughs, wiring tips, and shop-tested fixes — free.

No spam. Unsubscribe anytime.

Get AI-Guided Diagnosis for SPN 5829 FMI 31

The diagnostic engine walks you through every physical test — step by step, on your phone, at the truck. No guessing. No wasted parts.

Run Full DiagnosisView Related FaultsSee OEM System Guide