SPN 480 FMI 0AftertreatmentMedium
Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1
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Overview
Fault Code
SPN 480 / FMI 0
Category
Aftertreatment
Severity
Medium
Regen Inhibit
No
Inducement Risk
No
Component Location: Exhaust gas temperature sensor is mounted in the exhaust system upstream of the DPF, typically near the turbocharger outlet.
Common Symptoms
- Active fault code for EGT sensor Bank 1 Sensor 1
- EGT reading above expected range or pegged high
- DPF regeneration inhibited or interrupted
- Engine derate or reduced power condition
- Abnormally high exhaust temperature reading on gauge or dash display
- MIL or CEL illuminated
Root Causes
- Failed or degraded EGT sensor (open or short circuit causing high voltage/out of range high)
- Damaged or chafed wiring harness causing short to voltage
- Corroded or contaminated sensor connector
- Sensor exposed to excessive heat causing internal failure
- Water or moisture intrusion into connector
- Faulty ECM or aftertreatment control module (rare)
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Derate Behavior
Mileage / Regen Notes
FMI 0 (data valid but above normal range) on EGT Bank 1 Sensor 1 will typically inhibit or abort active DPF regeneration events, as the control module cannot safely verify exhaust temperatures. Passive regen may also be disabled depending on OEM calibration.
System Interactions
SPN 480 FMI 0 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 480 FMI 0 — 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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