SPN 3516 FMI 7HighInducement Risk
DEF Pump - Mechanical System Not Responding
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 3516 / FMI 7
Severity
High
Regen Inhibit
No
Inducement Risk
Yes — SCR inducement possible
Component Location: DEF pump is mounted on the DEF tank or nearby frame rail, connected to the DEF dosing system and SCR catalyst.
Common Symptoms
- No DEF pressure despite electrical OK, dosing failure
Root Causes
- DEF pump mechanical failure, frozen DEF, pump cavitation, filter clogged
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Derate Behavior
SCR Inducement Risk
If left unresolved, this fault may trigger SCR inducement — a progressive derate enforced by the ECM to ensure emissions compliance.
System Interactions
SPN 3516 FMI 7 interacts with the following systems and may trigger cascading faults if not resolved promptly.
TSB Reference: DEF pump mechanical TSBs
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.
OEM Notes
PACCAR
MX-13: Check for DEF crystallization in pump inlet
Cummins
Check DEF filter at pump; common failure on ISX15 >200k miles
Detroit
DD series: DEF pump module includes filter — replace as assembly
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 3516 FMI 7 — 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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