SPN 1248 FMI 7ABS
Wheel Speed Sensor - Rear Right Inner - Mechanical System Not Responding
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 1248 / FMI 7
Category
ABS
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The rear right inner wheel speed sensor is mounted on the differential or axle housing adjacent to the tone ring on the axle shaft.
Common Symptoms
- ABS warning light illuminated on dash
- Traction control system disabled or inactive
- Stability control malfunction indicator active
- Loss of ABS function during braking events
- Intermittent wheel speed signal dropout
Root Causes
- Damaged or missing tone ring on rear right inner axle Wheel speed sensor physical damage or misalignment Excessive air gap between sensor and tone ring Tone ring teeth worn or broken from debris impact Wheel bearing excessive play causing sensor clearance issues
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Derate Behavior
Power Derate
No
System Interactions
SPN 1248 FMI 7 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
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 1248 FMI 7 — 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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