SPN 3245 FMI 5AftertreatmentInducement Risk
Aftertreatment DEF Pump - Current Below Normal or Open Circuit
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Overview
Fault Code
SPN 3245 / FMI 5
Category
Aftertreatment
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
Yes — SCR inducement possible
Component Location: DEF pump is typically mounted on the DEF tank or nearby frame rail, connected to the ACM via a dedicated wiring harness routed along the chassis.
Common Symptoms
- DEF pump not operating or no DEF dosing
- Active DPF regeneration inhibited
- SCR system not reducing NOx
- MIL or amber warning lamp illuminated
- Derate or power reduction in some applications
- DEF system warning on dashboard
Root Causes
- Open circuit in DEF pump motor supply or return wiring harness
- Blown fuse in DEF pump power circuit
- Corroded or damaged connector at DEF pump
- Failed DEF pump motor (open winding internally)
- Chafed or broken wire between ACM and DEF pump
- Poor ground connection at DEF pump or ACM
- Failed ACM output driver for DEF pump circuit
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Derate Behavior
Power Derate
Yes
SCR Inducement Risk
If left unresolved, this fault may trigger SCR inducement — a progressive derate enforced by the ECM to ensure emissions compliance.
Mileage / Regen Notes
FMI 5 on SPN 3245 indicates the ACM detects current below normal or open circuit on the DEF pump circuit. DEF dosing will be disabled, SCR aftertreatment will not function, and active DPF regeneration may be inhibited or restricted. Prolonged fault condition may trigger NOx-related derates.
System Interactions
SPN 3245 FMI 5 interacts with the following systems and may trigger cascading faults if not resolved promptly.
DPF differential pressure monitoring — soot load calculations affected
SCR NOx conversion efficiency — DEF dosing strategy may be altered
Active regen inhibit logic — regen may be blocked or delayed
Engine protection derate — ECM may reduce power to protect components
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 the DPF without verifying the regen system is functional — a failed regen injector will reload the new DPF.
Ignoring DEF quality — contaminated DEF causes SCR efficiency faults that look like hardware failures.
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OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 3245 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.
EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx 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.
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