SPN 652 FMI 6Fuel SystemHigh
Injector Cylinder 2 - Current Above Normal
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Overview
Fault Code
SPN 652 / FMI 6
Category
Fuel System
Severity
High
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
No
Component Location: Cylinder 2 injector is mounted in the cylinder head at the second cylinder position, accessible from the valve cover area on top of the engine.
Common Symptoms
- Misfire on cylinder 2, rough running especially at idle, excessive black smoke under load, noticeable power loss, engine running rough or shaking, audible knock or uneven firing, possible white smoke at startup if injector is stuck open, elevated EGT on cylinder 2, fuel dilution in oil if injector fails open
Root Causes
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Derate Behavior
Power Derate
Yes
Mileage / Regen Notes
This fault typically does not directly inhibit active DPF regeneration. However, the cylinder misfire and uneven combustion may cause elevated soot loading or abnormal EGT readings that could affect regen efficiency. If additional faults set due to combustion imbalance, active regen may be postponed until repairs are made. Repair promptly to prevent secondary aftertreatment issues.
System Interactions
SPN 652 FMI 6 interacts with the following systems and may trigger cascading faults if not resolved promptly.
Fuel rail pressure — injector timing and quantity affected
Engine power output — derate may be triggered to protect injectors
Aftertreatment regen — low fuel pressure can prevent regen completion
TSB Reference: No confirmed TSBs — verify in OEM service portal. Check for manufacturer-specific bulletins related to injector harness chafing near valve cover or exhaust manifold heat shields. Cummins, Detroit, and Paccar have issued harness routing advisories for various model years.
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.
Replacing injectors without verifying fuel supply pressure — low supply pressure causes injector faults.
Ignoring fuel filter restriction — a clogged filter causes low rail pressure that mimics injector failure.
Related Faults in This Category
OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 652 FMI 6 — 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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