SPN 105 FMI 18Air System
Intake Manifold Pressure - Data Valid But Above Normal - Moderately Severe
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 105 / FMI 18
Category
Air System
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
No
Component Location: The intake manifold pressure sensor is typically mounted on the intake manifold between the turbocharger outlet and the engine intake ports.
Common Symptoms
- Engine power loss or derate
- Black smoke from exhaust
- Poor fuel economy
- Turbocharger overspeeding
- Check engine light illuminated
- Reduced boost pressure at high load
Root Causes
- Restricted air intake filter or ducting Turbocharger overboost condition Faulty intake manifold pressure sensor Wastegate actuator failure or binding EGR valve stuck closed
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Derate Behavior
Power Derate
Yes
System Interactions
SPN 105 FMI 18 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 105 FMI 18 — 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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