SPN 764 FMI 0Transmission
Transmission Control System MIL Request Circuit/Open
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
DieselVision™ Upload photos — DieselVision™ reads diagrams, connectors, and screens with precision.
Overview
Fault Code
SPN 764 / FMI 0
Category
Transmission
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: TCM is typically mounted on or near the transmission housing or in the cab chassis rail area; MIL request circuit runs through the main chassis harness to the ECM.
Common Symptoms
- Transmission warning or MIL lamp illuminated on dash
- Active fault code stored in TCM or ECM
- Possible limp-home or reduced gear range operation
- Harsh or erratic shifting behavior
- Transmission may not upshift beyond a limited gear
- Intermittent loss of communication between TCM and ECM
Root Causes
- TCM (Transmission Control Module) internal fault triggering MIL request to ECM via datalink Open or high-resistance circuit in the MIL request signal wire between TCM and ECM/BCM CAN/J1939 datalink communication fault causing loss of TCM MIL request signal Corroded or damaged connector pins at TCM harness connector TCM power supply or ground circuit fault causing erroneous MIL request
Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.
AI walks you through every test — one step at a time. Plans start at $12.95/mo.
Derate Behavior
Power Derate
No
System Interactions
SPN 764 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 764 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.
Get weekly diesel diagnostic tips
Real-world fault code walkthroughs, wiring tips, and shop-tested fixes — free.
No spam. Unsubscribe anytime.
Get AI-Guided Diagnosis for SPN 764 FMI 0
The diagnostic engine walks you through every physical test — step by step, on your phone, at the truck. No guessing. No wasted parts.