SPN 3242 FMI 6AftertreatmentMedium
DPF Outlet Temperature Sensor - Current Above Normal
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 3242 / FMI 6
Category
Aftertreatment
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: DPF outlet temperature sensor is mounted on the downstream (outlet) end of the diesel particulate filter canister, typically on the exhaust pipe just after the DPF body.
Common Symptoms
- Erratic DPF outlet temp reading
Root Causes
- Short circuit to ground in the DPF outlet temperature sensor signal wire causing excessive current draw Damaged or chafed wiring harness creating a low-resistance path to ground downstream of the sensor Failed DPF outlet temperature sensor with internal short circuit Corroded or water-intruded connector at the DPF outlet temperature sensor causing signal circuit short Damaged aftertreatment harness from heat exposure near DPF outlet causing insulation breakdown ECM/ACM sensor supply circuit fault providing incorrect reference voltage leading to overcurrent condition Connector backshell or seal failure allowing moisture ingress and creating short to chassis ground
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
Short circuit — inspect wiring before replacing sensor.
System Interactions
SPN 3242 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 3242 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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