SPN 1642 FMI 2ABS
ABS Retarder Control - Erratic/Intermittent
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 1642 / FMI 2
Category
ABS
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The ABS retarder control circuit connects the ABS control module typically mounted on the frame rail to the engine retarder control solenoid on the engine.
Common Symptoms
- ABS warning lamp illuminated on dash
- Erratic or intermittent engine retarder operation
- Loss of retarder functionality during braking events
- Intermittent ABS system faults during operation
- Engine retarder activates unpredictably or not at all
Root Causes
- Intermittent wiring or connector issues in ABS retarder control circuit Faulty ABS control module with intermittent output Loose or corroded connections at retarder control solenoid Damaged wiring harness between ABS module and engine retarder system Engine ECM not receiving consistent signals from ABS controller
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Derate Behavior
Power Derate
No
System Interactions
SPN 1642 FMI 2 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.
Related Faults in This Category
OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 1642 FMI 2 — 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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