SPN 1252 FMI 5ABS
ABS Modulator Valve - Rear Right - Current Below Normal
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 1252 / FMI 5
Category
ABS
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The rear right ABS modulator valve is mounted on the rear axle pneumatic ABS modulator assembly on the right side of the vehicle.
Common Symptoms
- ABS warning light illuminated
- Rear right wheel ABS inactive
- Wheel lockup during braking on rear right
- Reduced braking performance
- Traction control malfunction
Root Causes
- Open circuit in wiring harness to rear right ABS modulator valve Faulty rear right ABS modulator valve solenoid coil Corroded or damaged connector at rear right modulator valve Damaged or chafed wiring between ABS controller and rear right valve Faulty ABS electronic control unit output driver
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Derate Behavior
Power Derate
No
System Interactions
SPN 1252 FMI 5 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 1252 FMI 5 — 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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