SPN 598 FMI 3Brakes
Service Brake Circuit Pressure 2 - Voltage Above Normal
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 598 / FMI 3
Category
Brakes
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The secondary brake pressure sensor is typically mounted on the brake application valve or integrated into the ABS modulator assembly.
Common Symptoms
- ABS warning lamp illuminated
- Service brake malfunction indicator active
- Loss of ABS functionality
- Cruise control disabled
- Traction control disabled
- Stability control disabled
- Reduced braking performance warning
Root Causes
- Shorted brake pressure sensor or internal sensor failure Damaged wiring harness or chafed wires causing short to power Corroded or moisture-damaged sensor connector Faulty ABS module or ECU internal fault Incorrect sensor installation or mechanical damage to sensor
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Derate Behavior
Power Derate
No
System Interactions
SPN 598 FMI 3 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 598 FMI 3 — 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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