John Deere 639.12 – RLC (Roof Lighting Control Unit) / FCC (Front Console Control Unit): Vehicle CAN Bus (500 kBd), High Error Rate

The control unit is receiving an excessively high number of incorrect CAN Bus messages, or it detects a general communication failure on the primary Vehicle CAN Bus network.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 7210R
• 7230R
• 7250R
• 7270R
• 7290R
• 7310R
• 8225R
• 8245R
• 8270R
• 8295R
• 8320R
• 8335R
• 8345R
• 8370R
• 8400R
• 8320RT
• 8345RT
• 8370RT
• 9360R
• 9410R
• 9460R
• 9510R
• 9560R
• 9470RT
• 9520RT
• 9570RT

1. 1

   Restart the tractor and cycle the key switch to see if the transient CAN overflow code clears

2. 2

   Inspect the main Vehicle CAN Bus harness (especially routing up to the cab roof and front console) for chafing, damage, wear, or corrosion

3. 3

   Ensure all CAN Bus connectors plugging into the RLC and FCC are secure and free of debris or moisture

4. 4

   Identify and eliminate sources of electrical interference, ensuring proper grounding and shielding of the CAN Bus cables

5. 5

   Verify if the RLC and FCC control software versions are up to date

1. 1

   Disconnect Power

   Turn off the engine and disconnect the battery to prevent electrical shorts while working on the CAN network.

2. 2

   Clean and Re-seat Connectors

   Unplug the harnesses at the Roof Lighting Control Unit (RLC) and the Front Console Control Unit (FCC). Apply electrical contact cleaner, check for pushed-out pins, and firmly re-seat the connectors.

3. 3

   Repair Wiring

   If diagnostic checks revealed damaged wires or degraded shielding on the CAN High or CAN Low lines, splice and repair the wiring using OEM-approved waterproof connectors, or replace the affected harness section.

4. 4

   Isolate the Faulty Module

   If the wiring is intact but the bus remains overloaded, unplug modules one by one (starting with the RLC, then the FCC) to see if the CAN bus error rate drops. A module with an internal hardware failure will spam the network; identifying the culprit requires isolating them.

5. 5

   Replace the Module

   If the RLC or FCC is found to be internally shorted, replace the unit with a new or remanufactured part.

6. 6

   Update Software

   After replacing any module or repairing the bus, have a John Deere dealer flash the latest control software to ensure network stability.

7. 7

   Test

   Reconnect the battery, start the tractor, and verify that the 000639.12 code has moved from 'Active' to 'Stored' or cleared entirely.