Komatsu Fault Code

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SPN 3509 FMI 4

All Digging Telemetry Lost on Monitor

System

Electrical

Symptom

All Digging Telemetry Lost on Monitor

Diagnosis & fix steps

LOGIC: Sensor Supply 5V Reference 1 Circuit Low (Shorted to Ground). ACTION: Unplug shared 5V line sensors (MAP, rail pressure, oil temp) one by one until global 5V reference recovers on scan tool to isolate shorted transducer.

Red Seal field insights

Shared Rail Trap: An internal short to ground inside a single sensor collapses the entire shared 5V supply line array, blinding adjacent sensors simultaneously.

Same code keeps coming back?

That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.

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Read before you touch anything

  • This is general reference information, not a repair manual. It is for trained, qualified technicians.
  • Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
  • Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
  • You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
  • Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.

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