SPN 71 FMI 0Communication
Lost Communication with ECM/PCM A
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 71 / FMI 0
Category
Communication
Derate Risk
Yes
Regen Inhibit
No
Inducement Risk
No
Component Location: The ECM is typically mounted on the engine block or firewall with CAN bus connections to the vehicle network backbone.
Common Symptoms
- Check engine light illuminated
- Multiple system faults active simultaneously
- Loss of communication with engine control module
- Instrument cluster gauges erratic or non-functional
- Engine protection mode active
- Loss of cruise control and PTO functions
- Transmission shifting issues or limp mode
Root Causes
- Damaged or corroded CAN bus wiring between ECM and other modules Faulty ECM power or ground connections Failed ECM internal communication circuit Incorrect CAN bus termination resistors Water intrusion in ECM or CAN bus connectors
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Derate Behavior
Power Derate
Yes
System Interactions
SPN 71 FMI 0 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
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 71 FMI 0 — 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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