SPN 102 FMI 5Turbo / BoostMedium
Intake Manifold Pressure Sensor - Current Below Normal
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Overview
Fault Code
SPN 102 / FMI 5
Category
Turbo / Boost
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: Intake manifold pressure sensor is mounted directly on the intake manifold, typically on the top or side of the manifold, accessible from the top of the engine.
Common Symptoms
- Low or no boost pressure reading on gauge or datalink
- Engine derate or reduced power complaint
- MIL or Check Engine light illuminated
- Poor throttle response or sluggish acceleration
- Turbo over-boost due to missing sensor feedback
- DPF regen inhibited or disrupted
Root Causes
- Open circuit or broken wire in sensor signal or supply circuit
- Corroded or damaged connector at intake manifold pressure sensor
- Blown fuse or open in sensor 5V supply circuit
- Failed intake manifold pressure sensor (open internal element)
- Chafed or shorted wiring harness between sensor and ECM
- Poor ground connection at sensor or ECM ground reference
- ECM driver fault causing loss of sensor excitation
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
FMI 5 on SPN 102 will typically inhibit or disable active DPF regeneration because accurate intake manifold pressure is required to calculate airflow and manage regen fuel dosing; passive regen may also be impaired due to incorrect load calculations.
System Interactions
SPN 102 FMI 5 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 5 — 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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