AI Diesel Tech

Fault Code Reference

SPN 299 FMI 0BoostHigh

Turbocharger/Supercharger Underboost Condition

Run Full DiagnosisView Related FaultsSee OEM System Guide

Scan Tool — in guided session

DVOM Testing — in guided session

Connector Pinout — in guided session

DieselVision™ Upload photos — DieselVision™ reads diagrams, connectors, and screens with precision.

Overview

Fault Code

SPN 299 / FMI 0

Category

Boost

Severity

High

Regen Inhibit

No

Inducement Risk

No

Component Location: Turbocharger is mounted directly to the exhaust manifold on the engine, typically accessible from the top or side of the engine valley depending on configuration.

Common Symptoms

  • Low power or reduced engine performance under load
  • Black or excessive exhaust smoke during acceleration
  • Extended turbo spool-up time or sluggish throttle response
  • Boost pressure gauge reading below expected range
  • Engine derate or limp mode activation
  • Illuminated MIL or CEL with active SPN 299 FMI 0 fault

Root Causes

  • Intake or charge air system boost leak (intercooler, piping, couplers)
  • Turbocharger worn or damaged compressor/turbine wheel causing low boost output
  • Clogged or restricted air filter causing insufficient airflow to turbo
  • VGT actuator or variable geometry vane mechanism sticking or failed
  • Exhaust restriction (clogged DPF or collapsed catalytic substrate) reducing exhaust backpressure drive

Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.

AI walks you through every test — one step at a time. Plans start at $12.95/mo.

Start Guided DiagnosisSee How It Works

Derate Behavior

Mileage / Regen Notes

Active and parked DPF regeneration may be inhibited or interrupted when SPN 299 FMI 0 is active, as underboost conditions indicate insufficient exhaust energy or airflow needed to sustain regen temperatures; a clogged DPF may also contribute to the underboost condition itself.

System Interactions

SPN 299 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.

Deep-dive diagnostic page: SPN 299 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.

Get weekly diesel diagnostic tips

Real-world fault code walkthroughs, wiring tips, and shop-tested fixes — free.

No spam. Unsubscribe anytime.

Get AI-Guided Diagnosis for SPN 299 FMI 0

The diagnostic engine walks you through every physical test — step by step, on your phone, at the truck. No guessing. No wasted parts.

Run Full DiagnosisView Related FaultsSee OEM System Guide