AI Diesel Tech

Fault Code Reference

SPN 2659 FMI 6EGRMedium

EGR Target Error - Current Above Normal

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Overview

Fault Code

SPN 2659 / FMI 6

Category

EGR

Severity

Medium

Derate Risk

Sometimes

Regen Inhibit

No

Inducement Risk

No

Component Location: EGR mass flow calculated from MAP, MAT, and EGR valve position on ISX15; dedicated EGR flow sensor on DD15

Common Symptoms

  • EGR valve stuck open or over-responding
  • Excessive exhaust gas recirculation causing rough idle
  • Black smoke from excessive EGR flow
  • Engine hesitation or stumble under load
  • Reduced fuel economy
  • MIL or Check Engine lamp illuminated
  • Active fault logged in EGR control module

Root Causes

  • EGR valve actuator shorted to ground causing over-current condition Failed or shorted EGR valve solenoid winding Chafed or shorted wiring harness between ECM and EGR valve Faulty EGR valve position sensor providing incorrect feedback ECM driver circuit failure causing excess current output Carbon buildup causing EGR valve to bind open, overdriving actuator Corroded or water-intruded connector at EGR valve Failed EGR cooler causing thermal damage to valve assembly

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Derate Behavior

Power Derate

Sometimes

Mileage / Regen Notes

Short circuit — inspect wiring before replacing components.

System Interactions

SPN 2659 FMI 6 interacts with the following systems and may trigger cascading faults if not resolved promptly.

TSB Reference: EGR valve TSB

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 2659 FMI 6 — 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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