SPN 380 FMI 0Glow PlugsMedium
Glow Plug/Heater Circuit A
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 380 / FMI 0
Category
Glow Plugs
Severity
Medium
Regen Inhibit
No
Inducement Risk
No
Component Location: Glow plugs are threaded into the prechamber or combustion chamber of each cylinder head, accessible from the top of the engine near the valve cover.
Common Symptoms
- Hard starting in cold ambient temperatures
- Extended crank time before engine fires
- White smoke from exhaust on cold startup
- Glow plug warning light illuminated or not cycling off
- Rough idle immediately after cold start
- MIL or amber warning lamp active with SPN 380 FMI 0 logged
Root Causes
- One or more glow plugs failed open or shorted in Circuit A bank causing overcurrent or high resistance
- Glow plug relay or control module failure supplying Circuit A
- Corroded or damaged wiring harness connectors at glow plug Circuit A feed
- Individual glow plug element burnout due to age or excessive voltage
- Glow plug control module (GPCM) internal fault misreporting Circuit A current above threshold
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Derate Behavior
Mileage / Regen Notes
SPN 380 FMI 0 can inhibit or delay active DPF regeneration on cold starts; poor combustion quality from failed glow plugs increases soot load and may trigger elevated regen frequency or regen inhibit if misfire-adjacent conditions are detected.
System Interactions
SPN 380 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
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 380 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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