AI Diesel Tech

Fault Code Reference

SPN 1328 FMI 13Engine Protection

Misfire Cylinder 6 - Out of Calibration

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 1328 / FMI 13

Category

Engine Protection

Derate Risk

Yes

Regen Inhibit

No

Inducement Risk

No

Component Location: Cylinder 6 fuel injector is mounted in the cylinder head at the sixth cylinder position, accessible from the top valve cover side of the engine.

Common Symptoms

  • Rough idle or engine vibration
  • Loss of power or reduced engine performance
  • Increased fuel consumption
  • White or black smoke from exhaust
  • Engine runs rough under load
  • Cylinder 6 contribution test shows imbalance

Root Causes

  • Injector calibration code (IQA/ICUM trim code) not programmed or incorrectly programmed for cylinder 6
  • Injector replacement performed without reprogramming trim codes into ECM
  • Faulty or worn cylinder 6 fuel injector causing incorrect fuel delivery
  • Low compression on cylinder 6 due to worn rings, valves, or head gasket failure
  • Cylinder 6 injector return fuel leak causing low injection pressure
  • ECM software not updated after injector replacement
  • Contaminated or degraded fuel affecting injector atomization
  • Cylinder 6 injector wiring harness damage causing intermittent signal

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

Power Derate

Yes

System Interactions

SPN 1328 FMI 13 interacts with the following systems and may trigger cascading faults if not resolved promptly.

ECM communication — J1939 network faults can affect all connected modules
Engine protection — ECM may trigger derate to prevent damage
Aftertreatment — engine protection derates can affect regen strategy

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 1328 FMI 13 — 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 1328 FMI 13

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