SPN 3490 FMI 5Fuel System
High Pressure Fuel Pump Actuator - Current Below Normal or Open Circuit
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 3490 / FMI 5
Category
Fuel System
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
No
Component Location: High pressure fuel pump actuator is mounted on the high pressure common rail fuel pump, typically on the driver side of the engine block.
Common Symptoms
- Engine hard starting or no start condition
- Rough idle and poor engine performance
- Loss of power under load
- Black or white smoke from exhaust
- Engine may run but with reduced fuel rail pressure
- Check engine light illuminated
Root Causes
- Open circuit in high pressure fuel pump actuator wiring harness Faulty high pressure fuel pump actuator solenoid Corroded or damaged connector at fuel pump actuator ECM internal driver circuit failure Broken wire between ECM and high pressure fuel pump actuator
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Derate Behavior
Power Derate
Yes
System Interactions
SPN 3490 FMI 5 interacts with the following systems and may trigger cascading faults if not resolved promptly.
Fuel rail pressure — injector timing and quantity affected
Engine power output — derate may be triggered to protect injectors
Aftertreatment regen — low fuel pressure can prevent regen completion
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.
Replacing injectors without verifying fuel supply pressure — low supply pressure causes injector faults.
Ignoring fuel filter restriction — a clogged filter causes low rail pressure that mimics injector failure.
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OEM System Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 3490 FMI 5 — 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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