SPN 3516 FMI 2AftertreatmentInducement Risk
Exhaust Gas Temperature Bank 1 Sensor 1 - Data Erratic
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Overview
Fault Code
SPN 3516 / FMI 2
Category
Aftertreatment
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
Yes — SCR inducement possible
Component Location: Exhaust gas temperature sensor 1 is located in the exhaust system upstream of the diesel oxidation catalyst or turbocharger outlet.
Common Symptoms
- Check engine light illuminated
- DPF regeneration frequency increased or irregular
- Exhaust temperature readings fluctuating abnormally
- Intermittent fault code active/inactive cycling
- Poor regeneration performance or incomplete regens
- Engine derate or limited power in severe cases
Root Causes
- Faulty or degraded EGT sensor 1 (Bank 1) providing erratic/intermittent signal
- Damaged or corroded wiring harness between EGT sensor and ACM connector
- Loose or corroded sensor connector causing intermittent signal dropout
- Exhaust soot or moisture contamination on sensor element causing erratic readings
- Exhaust leak near sensor affecting accurate temperature measurement
- ACM software fault or calibration mismatch requiring reflash
- Failed ACM input circuit for EGT sensor signal
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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
SPN 3516 FMI 2 will typically inhibit or interrupt active DPF regeneration cycles as the ACM relies on EGT Bank 1 Sensor 1 to monitor and control regen temperatures; erratic data prevents safe regen execution and may trigger a regen inhibit or disable condition.
System Interactions
SPN 3516 FMI 2 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.
Related Faults in This Category
OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 3516 FMI 2 — 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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