SPN 190 FMI 3EngineMedium
Engine Speed Sensor - Voltage High
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 190 / FMI 3
Category
Engine
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: Engine speed sensor (crankshaft position sensor) is typically mounted on the engine block near the flywheel housing or front crankshaft timing cover, depending on OEM.
Common Symptoms
- Check engine light illuminated. Erratic or jumping RPM reading on dash and scan tool. Engine may start and immediately stall. Intermittent no-start condition. Tachometer reads higher than actual engine speed or pegged at max. Rough idle or surging. Loss of cruise control function. Transmission may not shift properly due to incorrect engine speed signal. Engine may run but with reduced power.
Root Causes
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Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
Active regeneration is typically inhibited while this fault is active. ECM requires accurate engine speed signal to safely manage regen fuel injection timing. If fault is intermittent, regen may initiate but abort if signal becomes erratic. Parked regen will not be allowed. Repair fault and clear code before attempting forced regen. No permanent aftertreatment damage expected from this fault alone.
System Interactions
SPN 190 FMI 3 interacts with the following systems and may trigger cascading faults if not resolved promptly.
TSB Reference: No confirmed TSBs — verify in OEM service portal. Check Cummins QuickServe for ISX/ISB sensor harness routing bulletins. Detroit Diesel has issued service letters regarding DD13/DD15 speed sensor connector sealing. Paccar MX engines have known harness chafe points near the front cover — check current service information.
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 190 FMI 3 — 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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