SPN 3563 FMI 2AftertreatmentInducement Risk
Exhaust Gas Temperature Bank 1 Sensor 2 - Data Erratic
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Overview
Fault Code
SPN 3563 / FMI 2
Category
Aftertreatment
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
Yes — SCR inducement possible
Component Location: The exhaust gas temperature sensor 2 is located in the exhaust system between the DPF outlet and the SCR catalyst inlet.
Common Symptoms
- Amber engine light illuminated
- Frequent or failed parked regenerations
- Exhaust temperature readings fluctuating abnormally
- High exhaust system backpressure warning
- DPF efficiency monitoring fault messages
- Check engine light with reduced power
Root Causes
- Damaged or corroded EGT sensor 2 connector at the DPF inlet/outlet position Failed or degraded EGT sensor 2 (open/short intermittently causing erratic signal) Chafed or damaged wiring harness between ACM and EGT sensor 2 Poor pin tension or corrosion at ACM harness connector Exhaust leak near sensor causing false erratic temperature readings Moisture intrusion into sensor connector causing intermittent signal ACM software issue or internal ACM fault (rare)
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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
Erratic EGT Bank 1 Sensor 2 data may inhibit or abort active DPF regeneration cycles, as the ACM relies on this sensor to monitor DPF inlet/outlet temperatures during regen. The system may lock out regen until a rational signal is restored, potentially leading to elevated DPF soot load and derate conditions.
System Interactions
SPN 3563 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 3563 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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