SPN 238 FMI 0Turbo
Turbocharger Boost Control A Range/Performance
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 238 / FMI 0
Category
Turbo
Derate Risk
Possible
Regen Inhibit
No
Inducement Risk
No
Component Location: Turbocharger is mounted on the exhaust manifold with the boost control actuator typically located on the turbocharger housing.
Common Symptoms
- Lack of engine power or acceleration
- Engine derate or limp mode activated
- Black smoke under load
- Turbocharger whistle or unusual noise
- Poor throttle response
- Check engine light illuminated
Root Causes
- Intake air leak between turbocharger and intake manifold Exhaust restriction or back pressure issue Turbocharger actuator malfunction or binding Variable geometry turbo mechanism sticking or carbon buildup Faulty boost pressure sensor or incorrect calibration
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Derate Behavior
Power Derate
Possible
System Interactions
SPN 238 FMI 0 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.
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 238 FMI 0 — 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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