SPN 411 FMI 4EGRMedium
EGR Differential Pressure - Voltage Low
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Overview
Fault Code
SPN 411 / FMI 4
Category
EGR
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: EGR differential pressure sensor is typically mounted on or near the EGR cooler or EGR valve assembly on the engine, with pressure hoses connecting to EGR inlet and outlet ports.
Common Symptoms
- Check engine light illuminated. MIL lamp on. Possible reduced engine power. EGR system may default to closed or fixed position. Slight increase in NOx emissions. Engine may run rough at idle. Poor fuel economy. Possible white or grey smoke at startup. EGR flow monitoring disabled by ECM.
Root Causes
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
This fault typically does NOT inhibit active DPF regeneration directly. The EGR differential pressure sensor is used primarily for EGR flow monitoring, not DPF soot load calculation. However, if the ECM cannot verify EGR flow, it may set the EGR system to a default state which can affect overall emissions strategy. If combined with other aftertreatment faults, regen may be postponed. Monitor for secondary faults that could inhibit regen.
System Interactions
SPN 411 FMI 4 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. Cummins ISX/ISB: Check for TSBs related to EGR delta P sensor harness routing and connector sealing. Detroit DD13/DD15: Check for service letters on aftertreatment harness chafing. Paccar MX: Review known issues with sensor connector corrosion in wet climates.
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
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 411 FMI 4 — 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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