SPN 647 FMI 14EGR
EGR Differential Pressure - Special Instructions
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 647 / FMI 14
Category
EGR
Derate Risk
Possible
Regen Inhibit
No
Inducement Risk
No
Component Location: EGR differential pressure sensor is mounted on or near the EGR cooler assembly, measuring pressure difference across the EGR system.
Common Symptoms
- Check engine light illuminated
- Engine derate or reduced power
- Increased fuel consumption
- Excessive black smoke during acceleration
- EGR system fault codes present
Root Causes
- Clogged or restricted EGR cooler Failed EGR differential pressure sensor Carbon buildup in EGR valve or passages Blocked or damaged differential pressure sensing lines Faulty EGR valve actuator or stuck valve
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Derate Behavior
Power Derate
Possible
System Interactions
SPN 647 FMI 14 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 647 FMI 14 — 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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