JD-SPN639-FMI14 serious John Deere PowerTech ›

J1939 Network - Lost Communication With ECU (CAN Bus Fault)

The JD-SPN639-FMI14 (John Deere PowerTech) diesel fault code means: J1939 Network - Lost Communication With ECU (CAN Bus Fault). This is a serious severity code.

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Keep driving?
No — stop driving
DIY difficulty
intermediate
Estimated cost
$40-$200 harness repair, $60-$150 resistor, $3K+ ECU
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Common Symptoms

  • Blank CommandCenter / dash panel
  • No engine RPM shown on display
  • Tractor may run at default speed or shut down

Probable Causes (Ranked by Likelihood)

  • Harness chafe at engine-cab pass-through rubbed through CAN pair Very Likely
  • Corroded 9-pin J1939 diagnostic connector Likely
  • Missing / failed terminating resistor (120 ohm) Possible
  • Failed ECU Less Likely

Frequently Asked Questions

What is John Deere fault code SPN 639 FMI 14?

On John Deere PowerTech engines, SPN 639 FMI 14 means: J1939 Network - Lost Communication With ECU (CAN Bus Fault). Serious code -- address promptly to avoid inducement / further damage.

Can I keep using my John Deere tractor with SPN 639 FMI 14?

Serious fault -- you can move the machine to a shop but don't run it under load. Diagnose with John Deere Service ADVISOR via an EDL v3 / CF3 interface.

How much does it cost to fix John Deere SPN 639 FMI 14?

Repair cost range: $40-$200 harness repair, $60-$150 resistor, $3K+ ECU. Dealer labor on large tractors runs $180-$240/hr in 2026.

Mechanics Guide Step-by-step diagnosis

Step-by-Step Diagnostic Procedure

  1. Measure 60 ohms across CAN-H / CAN-L with key off -- if 120 ohm, one terminator is missing.

  2. Wiggle-test harness at firewall / grille pass-through with Service ADVISOR live.

Sources 1

This page is built from documented references. Verify against your own service info before repair work.

  • SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)

Commonly Affected Vehicles

  • 2014+ John Deere 6R Series tractors
  • 2015+ John Deere 7R Series tractors
  • 2015+ John Deere 8R / 8RT Series tractors
  • 2015+ John Deere 9R / 9RT / 9RX Series tractors
  • 2015+ John Deere S670 / S680 / S690 combines
  • John Deere S770 / S780 / S790 combines
  • John Deere 544/644/724 wheel loaders (construction)
  • John Deere 310/410 backhoes

Explore More

More John Deere PowerTech codes → Diesel home All diesel codes Heavy-duty Guides

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