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Fault Code Reference

SPN 411 FMI 3EGRMedium

EGR Differential Pressure - Voltage High

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Overview

Fault Code

SPN 411 / FMI 3

Category

EGR

Severity

Medium

Derate Risk

Sometimes

Regen Inhibit

No

Inducement Risk

No

Component Location: The EGR differential pressure sensor is typically mounted on or near the EGR cooler or intake manifold to measure pressure drop across the EGR system.

Common Symptoms

  • Check engine light illuminated. EGR system malfunction warning. Possible reduced engine power or torque. Poor fuel economy. Elevated NOx emissions. EGR valve may default to closed position. Rough idle in some cases. Scan tool shows EGR differential pressure reading pegged at maximum value.

Root Causes

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Derate Behavior

Power Derate

Sometimes

Mileage / Regen Notes

This fault alone typically does not inhibit active DPF regeneration. However, if the ECM cannot accurately calculate EGR flow, it may limit regen frequency or duration to protect emissions compliance. If combined with other EGR or aftertreatment faults, active regen may be disabled. Monitor for elevated soot loading if fault is present long-term.

System Interactions

SPN 411 FMI 3 interacts with the following systems and may trigger cascading faults if not resolved promptly.

TSB Reference: No confirmed universal TSBs — verify in OEM service portal. Check OEM-specific bulletins for EGR delta-P sensor connector corrosion issues and harness routing updates. Cummins, Detroit, and Paccar have issued service letters on EGR sensor wiring damage from exhaust heat — search by engine serial number.

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 411 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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