SPN 4240 FMI 3Turbo
Turbocharger 1 Compressor Intake Temperature - Voltage Above Normal
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 4240 / FMI 3
Category
Turbo
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The compressor intake temperature sensor is located at the turbocharger compressor inlet or intake air duct upstream of the compressor wheel.
Common Symptoms
- Check engine light illuminated
- Reduced engine power or boost pressure limitation
- Elevated intake air temperature reading displayed
- Turbocharger underboost condition
- Engine derate active or pending
Root Causes
- Open circuit in compressor intake temperature sensor wiring harness Faulty turbocharger compressor intake temperature sensor Corroded or damaged connector at temperature sensor Chafed or broken wiring between sensor and ECM Failed ECM supply circuit to sensor
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Derate Behavior
Power Derate
No
System Interactions
SPN 4240 FMI 3 interacts with the following systems and may trigger cascading faults if not resolved promptly.
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.
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OEM System Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 4240 FMI 3 — 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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