SPN 1243 FMI 10ABS
Wheel Speed Sensor - Front Left - Abnormal Rate of Change
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 1243 / FMI 10
Category
ABS
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The front left wheel speed sensor is mounted at the front left wheel hub assembly, typically near the brake caliper or spindle.
Common Symptoms
- ABS warning lamp illuminated on dash
- ABS system disabled or non-functional
- Intermittent speedometer fluctuation
- Traction control disabled message
- Stability control system inactive
Root Causes
- Damaged or corroded wheel speed sensor wiring harness Faulty front left wheel speed sensor Tone ring damage or debris accumulation Intermittent sensor air gap due to bearing wear ABS ECU internal fault
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Derate Behavior
Power Derate
No
System Interactions
SPN 1243 FMI 10 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.
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OEM System Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 1243 FMI 10 — 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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