SPN 102 FMI 2Turbo / BoostMedium
Intake Manifold Pressure - Data Erratic
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Overview
Fault Code
SPN 102 / FMI 2
Category
Turbo / Boost
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: MAP sensor is typically mounted directly on the intake manifold or charge air crossover pipe, accessible from the top or side of the engine near the turbocharger outlet.
Common Symptoms
- Erratic or fluctuating boost pressure gauge readings
- Intermittent check engine light or amber warning lamp
- Inconsistent engine power output
- Poor throttle response or hesitation under load
- Intermittent low power or derate events
- DPF regen interruptions or incomplete regeneration cycles
- Surging or hunting at steady throttle
Root Causes
- Faulty or contaminated MAP (manifold absolute pressure) sensor
- Loose, cracked, or damaged boost pressure sensor wiring harness connector
- Chafed or intermittently open/short circuit in sensor signal wire
- Air leak at intake manifold, charge air cooler, or boost tube connection
- Moisture or oil contamination in sensor port or connector
- Failed MAP sensor with internal intermittent fault
- Clogged or restricted sensor pressure port or hose
- ECM/ECU software or calibration issue causing erratic signal interpretation
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
Erratic MAP data can interrupt or inhibit active DPF regeneration. The ECM may abort an in-progress regen if boost pressure signal is unreliable, as accurate MAP data is required to calculate exhaust flow and dosing rates. Passive regen may also be compromised under inconsistent boost conditions.
System Interactions
SPN 102 FMI 2 interacts with the following systems and may trigger cascading faults if not resolved promptly.
TSB Reference: Boost sensor TSB
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 102 FMI 2 — 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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