SPN 2 FMI 0Air Intake
Mass or Volume Air Flow Circuit Low
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 2 / FMI 0
Category
Air Intake
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The mass air flow sensor is typically mounted in the intake air duct between the air filter housing and the turbocharger inlet.
Common Symptoms
- Black smoke from exhaust under load
- Loss of power and poor acceleration
- Rough idle or unstable engine operation
- Check engine light illuminated
- Increased fuel consumption
- Turbocharger overboost conditions
- Poor throttle response
Root Causes
- Faulty mass air flow sensor Air intake restriction or blockage Wiring harness damage or poor connection at MAF sensor Contaminated or dirty MAF sensor element Intake air leak upstream of MAF sensor
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Derate Behavior
Power Derate
No
System Interactions
SPN 2 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
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 2 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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