SPN 335 FMI 0TimingHigh
Crankshaft Position Sensor A Circuit Range/Performance
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 335 / FMI 0
Category
Timing
Severity
High
Regen Inhibit
No
Inducement Risk
No
Component Location: Crankshaft Position Sensor A is typically mounted on the engine block near the front or rear of the crankshaft, adjacent to the reluctor/tone ring.
Common Symptoms
- Hard start or no-start condition
- Engine stall at idle or low RPM
- Rough or erratic engine running
- MIL or Check Engine light illuminated
- Engine hesitation or stumble under load
- Intermittent loss of power
Root Causes
- Excessive crankshaft reluctor wheel runout or damaged tone ring teeth
- Improper air gap between CKP sensor and reluctor wheel
- CKP sensor contaminated with metallic debris or oil
- Wiring harness damage, chafing, or connector corrosion causing signal noise
- Worn crankshaft main bearings causing excessive crank movement
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Derate Behavior
Mileage / Regen Notes
SPN 335 FMI 0 can inhibit or abort active DPF regeneration due to unreliable engine timing data; ECM may also derate engine power and restrict regen initiation until fault is resolved.
System Interactions
SPN 335 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
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 335 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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