SPN 404 FMI 0EGR
EGR Control Circuit Range/Performance
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
DieselVision™ Upload photos — DieselVision™ reads diagrams, connectors, and screens with precision.
Overview
Fault Code
SPN 404 / FMI 0
Category
EGR
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: EGR valve is mounted on the intake manifold or intake side of the engine with electrical connector and vacuum/pneumatic lines.
Common Symptoms
- EGR valve position does not match commanded position under load
- Excessive black or white smoke from exhaust during acceleration
- Engine derate or reduced power mode active
- Elevated NOx readings or failed emissions test
- Rough idle or unstable idle when EGR system is active
- MIL or CEL illuminated with active or stored SPN 404 FMI 0 fault
Root Causes
- EGR valve stuck open or mechanically binding due to carbon/soot buildup preventing proper position feedback EGR valve position sensor (potentiometer) out of range or drifted, reporting actual position exceeds commanded position limits EGR cooler restriction or failure causing excessive backpressure affecting EGR flow performance and control authority EGR actuator (pneumatic, electric, or hydraulic) unable to achieve commanded position due to mechanical wear or actuator failure Exhaust differential pressure sensor or EGR mass flow sensor out of calibration causing erroneous performance feedback
Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.
AI walks you through every test — one step at a time. Plans start at $12.95/mo.
Derate Behavior
Power Derate
No
Mileage / Regen Notes
SPN 404 FMI 0 (data valid but above normal range) can inhibit or delay active DPF regeneration. EGR over-flow conditions may cause improper exhaust temperature management, leading the ECM to suspend regen to protect the aftertreatment system. Derates may also be applied.
System Interactions
SPN 404 FMI 0 interacts with the following systems and may trigger cascading faults if not resolved promptly.
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 404 FMI 0 — 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.
Get weekly diesel diagnostic tips
Real-world fault code walkthroughs, wiring tips, and shop-tested fixes — free.
No spam. Unsubscribe anytime.
Get AI-Guided Diagnosis for SPN 404 FMI 0
The diagnostic engine walks you through every physical test — step by step, on your phone, at the truck. No guessing. No wasted parts.