SPN 1087 FMI 4ABS
Secondary Brake Application Pressure - Voltage Below Normal
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 1087 / FMI 4
Category
ABS
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: Secondary brake pressure sensor is typically mounted on the brake application valve or treadle valve assembly in the cab area.
Common Symptoms
- Secondary brake application pressure reading zero or very low
- ABS warning lamp illuminated on dash
- Brake application pressure gauge shows incorrect low reading
- Traction control may be disabled or limited
- Stability control system may not function properly
- No secondary brake pressure indication on diagnostic tool
Root Causes
- Faulty secondary brake pressure sensor Damaged wiring harness or connector to secondary brake pressure sensor Corroded or loose connector pins at sensor Short to ground in secondary brake pressure sensor circuit Faulty ABS ECU or internal controller issue
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Derate Behavior
Power Derate
No
System Interactions
SPN 1087 FMI 4 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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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 1087 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.
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