SPN 630 FMI 9Network
J1939 Network #2 - Abnormal Update Rate
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 630 / FMI 9
Category
Network
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: J1939 Network #2 refers to the secondary CAN bus connecting ECM, transmission, instrument cluster, and other vehicle control modules.
Common Symptoms
- Intermittent communication loss with modules on secondary J1939 network
- Missing or delayed parameter messages from connected components
- Instrument cluster displays missing data or dashes intermittently
- Multiple module communication fault codes present
- Engine management system functions intermittently
- Transmission or body controller communication errors
Root Causes
- Loss of communication or missing messages on J1939 secondary data link (CAN bus #2)
- Damaged, corroded, or loose J1939 network connector or backbone termination resistor
- Missing or incorrect 120-ohm termination resistor at one or both ends of CAN bus #2
- Open or short circuit in CAN High or CAN Low wiring on J1939 Network #2
- Faulty or non-responsive node broadcasting on J1939 Network #2 (e.g., TCM, ABS, body controller)
- Incorrect baud rate or network configuration mismatch between modules
- ECM software or calibration mismatch causing CAN bus timing errors
- Failing or intermittently responsive ECM CAN transceiver
- Excessive network load or bus-off condition caused by a rogue module
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Derate Behavior
Power Derate
No
System Interactions
SPN 630 FMI 9 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 630 FMI 9 — 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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