AI Diesel Tech

Fault Code Reference

SPN 242 FMI 0Turbocharger

Turbocharger/Supercharger Wastegate Control A

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Overview

Fault Code

SPN 242 / FMI 0

Category

Turbocharger

Derate Risk

Yes

Regen Inhibit

No

Inducement Risk

No

Component Location: The wastegate actuator is mounted on the turbocharger housing, typically on the hot or cold side depending on turbo design.

Common Symptoms

  • Check engine light illuminated
  • Excessive black smoke from exhaust
  • Reduced engine power and acceleration
  • High boost pressure readings
  • Overboost condition reported
  • Turbocharger overboosting during load
  • Engine derating or limp mode activated

Root Causes

  • Faulty wastegate actuator or seized wastegate linkage Wastegate control solenoid valve failure Air leak in wastegate pneumatic or vacuum control lines Turbocharger wastegate stuck open or closed ECM commanded wastegate position not achieved due to mechanical binding

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Derate Behavior

Power Derate

Yes

System Interactions

SPN 242 FMI 0 interacts with the following systems and may trigger cascading faults if not resolved promptly.

Boost pressure — engine air/fuel ratio and power output affected
EGR system — boost pressure affects EGR flow calculations
Aftertreatment — low boost can cause incomplete combustion and DPF loading

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 242 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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