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Fault Code Reference

SPN 2791 FMI 5EGRMedium

EGR Valve - Current Below Normal

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Overview

Fault Code

SPN 2791 / FMI 5

Category

EGR

Severity

Medium

Derate Risk

Sometimes

Regen Inhibit

No

Inducement Risk

No

Component Location: EGR valve is mounted on the intake manifold or EGR cooler outlet on the engine, typically on the driver side or front of the engine block.

Common Symptoms

  • EGR valve not responding to commanded position, check engine light illuminated, reduced engine power or torque, rough idle or surging at idle, increased black smoke under load, poor fuel economy, engine may run hotter than normal due to lack of EGR flow, possible limp mode activation on some applications

Root Causes

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Derate Behavior

Power Derate

Sometimes

Mileage / Regen Notes

This fault typically does not directly inhibit active DPF regeneration. However, if the EGR valve cannot be controlled, the engine may not achieve proper exhaust temperatures or air management conditions for efficient regen. Monitor for related codes that may inhibit regen. In most cases, active regen is still allowed but may be less effective.

System Interactions

SPN 2791 FMI 5 interacts with the following systems and may trigger cascading faults if not resolved promptly.

TSB Reference: No confirmed TSBs — verify in OEM service portal. Check for service bulletins related to EGR valve harness routing and chafing points, particularly near exhaust components and frame rails where heat and vibration cause wire damage.

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 2791 FMI 5 — 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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