SPN 2791 FMI 3EGRMedium
EGR Valve Position - Voltage High
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 2791 / FMI 3
Category
EGR
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: EGR valve is mounted on the engine intake or exhaust crossover passage, typically on the driver side or front of the engine block near the intake manifold.
Common Symptoms
- Check engine light illuminated. EGR position sensor reading pegged high or at maximum value (near 100%) on scan tool. Reduced engine power or torque in some cases. Poor throttle response. Possible black smoke due to improper EGR flow control. Engine may run rough at idle. Fuel economy decrease. EGR valve may not respond to commanded position changes.
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 ECM cannot accurately control EGR position due to this fault, exhaust temperatures and oxygen levels may be affected, which can indirectly impact regen efficiency. The ECM may use a default EGR position strategy allowing regens to continue. Monitor regen performance after repair to ensure proper operation.
System Interactions
SPN 2791 FMI 3 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 harness routing bulletins specific to your engine platform (Cummins ISX/X15, DD13/DD15, Paccar MX). Some manufacturers have issued service letters regarding EGR harness chafing near turbo and exhaust manifold heat shields.
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.
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 2791 FMI 3 — 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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