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Fault Code Reference

SPN 3700 FMI 13AftertreatmentInducement Risk

Aftertreatment 1 Diesel Oxidation Catalyst - Out of Calibration

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Overview

Fault Code

SPN 3700 / FMI 13

Category

Aftertreatment

Derate Risk

Possible

Regen Inhibit

No

Inducement Risk

Yes — SCR inducement possible

Component Location: DOC is located in the aftertreatment assembly mounted on or near the turbocharger exhaust outlet, upstream of the DPF, typically on the driver-side of the engine compartment or under-cab tunnel.

Common Symptoms

  • Check engine light illuminated
  • Engine derate or power reduction
  • Elevated exhaust temperatures
  • Increased fuel consumption
  • Regeneration cycles more frequent than normal
  • DOC inefficiency detected by system

Root Causes

  • DOC catalyst substrate degraded or poisoned (oil ash, sulfur, phosphorus contamination) DOC inlet or outlet temperature sensor out of calibration or failed Incorrect DOC installed (wrong catalyst formulation or substrate volume for engine application) Exhaust leaks upstream or downstream of DOC affecting temperature differential readings Extended idle or low-load operation causing DOC deactivation and thermal degreening ACM software or calibration file mismatch requiring reflash Fuel quality issues causing sulfur poisoning of catalyst Improper previous repair using aftermarket or non-OEM DOC substrate

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Derate Behavior

Power Derate

Possible

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 3700 FMI 13 indicates the DOC is out of calibration or performing outside expected efficiency parameters. Active regeneration may be inhibited or incomplete because the ACM cannot confirm proper DOC exotherm to initiate or sustain DPF passive or active regen. The system may command multiple forced regens with limited effectiveness. Regen inhibit conditions may escalate to DPF loading faults if the DOC efficiency issue is unresolved.

System Interactions

SPN 3700 FMI 13 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.

Deep-dive diagnostic page: SPN 3700 FMI 13 — 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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