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Fault Code Reference

SPN 4360 FMI 2Medium

SCR Intake Gas Temperature - Data Erratic

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Overview

Fault Code

SPN 4360 / FMI 2

Severity

Medium

Regen Inhibit

No

Inducement Risk

No

Component Location: SCR inlet temperature sensor is mounted on the exhaust pipe immediately upstream of the SCR catalyst brick, typically within the aftertreatment assembly under or behind the cab.

Common Symptoms

  • SCR intake temperature sensor reading erratic or fluctuating abnormally
  • Intermittent fault codes with no consistent pattern
  • DEF dosing irregularities or incorrect SCR efficiency
  • Active or pending fault code SPN 4360 FMI 2
  • Possible DPF regen inhibit or incomplete regen events
  • Dashboard aftertreatment warning lamp illuminated

Root Causes

  • Damaged, corroded, or loose wiring harness connector at SCR inlet temperature sensor
  • Chafed or shorted wiring between sensor and aftertreatment control module (ACM)
  • Faulty SCR inlet temperature sensor providing intermittent signal
  • Poor ground connection at sensor or ACM
  • Moisture or contamination intrusion into sensor connector
  • ACM internal fault or software issue causing erratic data interpretation
  • Exhaust system heat damage to wiring harness near SCR inlet

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Derate Behavior

Mileage / Regen Notes

Erratic SCR inlet temperature data may inhibit or interrupt active DPF regeneration events, as the ACM relies on accurate exhaust temperature readings to manage regen strategy and DEF dosing. Incomplete regens can result in DPF soot accumulation.

System Interactions

SPN 4360 FMI 2 interacts with the following systems and may trigger cascading faults if not resolved promptly.

TSB Reference: Temp sensor TSB

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.

Deep-dive diagnostic page: SPN 4360 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.

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.EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx standards.

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