SPN 3246 FMI 6AftertreatmentMedium
DPF Outlet Temperature 2 Sensor - Current Above Normal
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 3246 / FMI 6
Category
Aftertreatment
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: DPF outlet temperature sensor 2 is mounted on the downstream face of the diesel particulate filter, typically on the exhaust pipe exiting the DPF canister.
Common Symptoms
- Erratic DPF outlet temp 2 reading
Root Causes
- Short circuit to ground or high current draw in the DPF outlet temperature sensor 2 signal circuit wiring Damaged, chafed, or melted wiring harness causing short to power or ground near the sensor Failed DPF outlet temperature sensor 2 with internal short circuit causing excessive current Corroded or moisture-contaminated connector at the DPF outlet temperature sensor 2 Pinched or abraded wiring harness routed too close to exhaust components causing insulation breakdown Faulty ECM or aftertreatment control module output driver providing excessive current to sensor circuit Incorrect sensor installed (wrong resistance/type) causing overcurrent condition
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
Short circuit — inspect wiring before replacing sensor.
System Interactions
SPN 3246 FMI 6 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
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 3246 FMI 6 — 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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