SPN 2659 FMI 9TurbochargerHigh
Turbocharger VGT Position — Abnormal Update Rate
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 2659 / FMI 9
Category
Turbocharger
Fault Type
actuator
FMI Category
abnormal rate
Severity
High
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
No
Component Location: VGT actuator on turbocharger — typically passenger side of engine.
Common Symptoms
- VGT position feedback not updating in live data
- Boost pressure erratic or uncontrolled
- Engine derate under load
- VGT position reading frozen or updating slowly
Root Causes
- VGT actuator position sensor failure
- VGT actuator communication fault — J1939 or PWM signal issue
- VGT actuator wiring — intermittent fault
- VGT actuator internal failure
- ECM VGT driver fault
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Derate Behavior
Power Derate
Yes
Mileage / Regen Notes
VGT actuator failure common at 400k–600k miles.
System Interactions
SPN 2659 FMI 9 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
TSB Reference: Cummins TSB 4021834 — VGT Actuator Diagnosis and Replacement
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.
OEM Notes
Cummins
X15: VGT actuator position feedback is critical for boost control. Frozen feedback causes ECM to default to fixed VGT position.
Detroit
DD15: VGT actuator uses CAN communication. DDDL required for full actuator diagnosis.
PACCAR
MX-13: VGT actuator position sensor is integral to actuator assembly — replace as unit.
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 2659 FMI 9 — 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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