SPN 340 FMI 0TimingHigh
Camshaft Position Sensor A Circuit (Bank 1)
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 340 / FMI 0
Category
Timing
Severity
High
Regen Inhibit
No
Inducement Risk
No
Component Location: Camshaft position sensor A Bank 1 is typically mounted on the front or side of the engine block or cylinder head near the camshaft gear or timing cover.
Common Symptoms
- Hard start or no-start condition
- Engine stalling at idle or low RPM
- Rough or erratic engine idle
- Reduced engine power or derating
- MIL or Check Engine lamp illuminated
- Intermittent misfire or rough running under load
Root Causes
- Camshaft position sensor failure (internal open or short)
- Reluctor wheel damage, debris buildup, or excessive air gap
- Wiring harness chafing, open circuit, or connector corrosion at sensor
- ECM/ECU internal fault causing loss of camshaft signal processing
- Timing component wear causing signal out of expected range
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Derate Behavior
Mileage / Regen Notes
SPN 340 FMI 0 can inhibit or abort active DPF regeneration cycles due to unreliable engine timing data; regen will not initiate or will be suspended until fault is resolved and cleared.
System Interactions
SPN 340 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
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 340 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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