SPN 190 FMI 4EngineMedium
Engine Speed Sensor - Voltage Low
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
DieselVision™ Upload photos — DieselVision™ reads diagrams, connectors, and screens with precision.
Overview
Fault Code
SPN 190 / FMI 4
Category
Engine
Severity
Medium
Derate Risk
Sometimes
Regen Inhibit
No
Inducement Risk
No
Component Location: Engine crankshaft position/speed sensor is typically mounted on the engine block near the crankshaft reluctor ring, often on the front or rear of the block depending on OEM.
Common Symptoms
- Check engine light illuminated. Tachometer reads zero or erratic RPM while engine is running. Engine may crank but not start (ECM cannot confirm engine speed). Intermittent stalling or rough running. Loss of cruise control function. Possible limp mode or reduced power. Speedometer may also be affected on some applications if signal is shared.
Root Causes
- [object Object]
- [object Object]
- [object Object]
- [object Object]
- [object Object]
- [object Object]
Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.
AI walks you through every test — one step at a time. Plans start at $12.95/mo.
Derate Behavior
Power Derate
Sometimes
Mileage / Regen Notes
Active DPF regeneration is typically inhibited when this fault is active. The ECM requires a valid engine speed signal to monitor and control regen temperatures safely. If the signal is intermittent, regen may abort mid-cycle. Parked regen will also be blocked on most platforms. Fault must be resolved and code cleared before regen can complete. Extended driving with this fault can lead to high soot load and eventual derate for DPF condition.
System Interactions
SPN 190 FMI 4 interacts with the following systems and may trigger cascading faults if not resolved promptly.
TSB Reference: No confirmed universal TSBs — verify in OEM service portal. Cummins ISX/ISB: check for TSBs related to engine harness chafing near bell housing. Detroit DD13/DD15: check for sensor connector sealing issues. Paccar MX: check for tone ring and sensor gap TSBs. Always search by engine serial number for applicable bulletins.
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 4 — 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.
Get weekly diesel diagnostic tips
Real-world fault code walkthroughs, wiring tips, and shop-tested fixes — free.
No spam. Unsubscribe anytime.
Get AI-Guided Diagnosis for SPN 190 FMI 4
The diagnostic engine walks you through every physical test — step by step, on your phone, at the truck. No guessing. No wasted parts.