SPN 522 FMI 2TransmissionMedium
Transmission Current Gear — Erratic
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 522 / FMI 2
Category
Transmission
Fault Type
sensor
FMI Category
data erratic
Severity
Medium
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: Transmission range sensor — on transmission shift tower or external
Common Symptoms
- Transmission gear position erratic
- Shift quality poor
- Transmission hunting between gears
- Gear indicator incorrect
Root Causes
- Transmission range sensor fault
- Wiring harness damage
- TCM fault
- Shift linkage adjustment
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Derate Behavior
Power Derate
No
Mileage / Regen Notes
Range sensor failure common at 200k–400k miles.
System Interactions
SPN 522 FMI 2 interacts with the following systems and may trigger cascading faults if not resolved promptly.
TSB Reference: Allison TSB 2019-003 — Transmission Range Sensor Diagnosis
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.
OEM Notes
Allison
Allison: Range sensor calibration may be required after replacement.
Eaton
Fuller: Check shift linkage adjustment before condemning sensor.
Meritor
Check connector for corrosion.
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OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 522 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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