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Fault Code Reference

SPN 27 FMI 2Medium

EGR Valve Position - Data Erratic

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Overview

Fault Code

SPN 27 / FMI 2

Severity

Medium

Regen Inhibit

No

Inducement Risk

No

Component Location: EGR valve is mounted on the intake manifold or intake side of the engine, connected to the exhaust gas recirculation system.

Common Symptoms

  • EGR valve position signal erratic or fluctuating
  • Rough idle or unstable engine operation
  • Increased NOx emissions
  • MIL or Check Engine light illuminated
  • DPF regeneration frequency increased
  • Poor fuel economy
  • Engine hesitation or stumble under load
  • Possible hard start condition

Root Causes

  • Faulty or contaminated EGR valve position sensor
  • Carbon buildup on EGR valve causing erratic feedback signal
  • Damaged or corroded EGR valve position sensor wiring or connector
  • Intermittent short or open in signal wire to EGR position sensor
  • Failed or sticking EGR valve actuator
  • Excessive soot or oil contamination in EGR passages affecting valve travel
  • ECM/EGR module software fault or calibration issue
  • Failed EGR cooler causing thermal damage to valve assembly

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Derate Behavior

Mileage / Regen Notes

Erratic EGR valve position may inhibit or delay active DPF regeneration due to improper exhaust gas recirculation affecting combustion and exhaust temperature targets; regen may be inhibited if ECM detects EGR system fault.

System Interactions

SPN 27 FMI 2 interacts with the following systems and may trigger cascading faults if not resolved promptly.

TSB Reference: EGR position TSBs

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.

Deep-dive diagnostic page: SPN 27 FMI 2 — 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.

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.EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx standards.

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