John Deere 639.14 – ETC: Vehicle CAN BUS, Very High Error Rate

The control unit is detecting an excessive number of incorrect CAN BUS messages or a general connectivity failure on the network. When the error rate exceeds a specific threshold, the module may enter a "Bus Off" state to prevent data corruption, which disables or reduces the functionality of the systems relying on that communication. Causes typically include electrical interference, faulty wiring, missing termination resistors, or a defective module flooding the network with bad data.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5000 series
• 6030 series
• 7030 series
• 6R series
• 7R series
• 8R series
• 9500
• 9600
• 9650 STS
• 9750 STS
• 450J
• 750J
• loaders
• excavators
• 6230
• 6330
• 6430
• 7130
• 7230
• 7430
• 7530

1. 1

   Visual Inspection: Inspect all CAN BUS wiring and connectors leading to the ETC module in the cab console/armrest. Look for signs of chafing, corrosion, or loose pins.

2. 2

   Resistance Test (Power Off): Disconnect the battery. Measure the resistance across the CAN High and CAN Low pins at the diagnostic port. A healthy CAN bus should read approximately 60 ohms (indicating two 120-ohm termination resistors are intact and wired in parallel). If it reads 120 ohms, there is a break in the wiring or a missing/failed termination resistor.

3. 3

   Voltage Test (Power On): Check the voltage levels on the CAN lines. In a standard John Deere J1939 network, recessive mode should show both wires at ~2.5V. In dominant mode, CAN High rises to ~3.75V, and CAN Low drops to ~1.25V.

4. 4

   Module Isolation: If the bus is crashing, disconnect modules one by one (starting with the ETC) to see if the network error rate drops. If disconnecting the ETC restores communication to the rest of the tractor, the ETC module has an internal hardware failure.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical damage.

2. 2

   Access the ETC

   Remove the cab trim panels to access the Electronic Temperature Control panel/module.

3. 3

   Inspect and Clean

   Disconnect the wiring harness from the ETC. Inspect the harness pins for fretting, corrosion, or pushed-back terminals. Clean with electronic contact cleaner.

4. 4

   Repair Wiring

   If your diagnostic checks revealed a wiring fault (e.g., a broken CAN wire or a burnt 120-ohm termination resistor), repair the harness or splice in a new resistor.

5. 5

   Replace/Repair the Module

   If the wiring and network integrity are verified as good, but the ETC module continues to trigger the 000639.14 code, the ETC control unit itself has an internal EEPROM or CAN transceiver failure. You must replace it or send it to an agricultural electronics specialist for board-level repair.

6. 6

   Reassembly

   Install the new or repaired ETC module and reconnect the harness.

7. 7

   Clear Codes

   Reconnect the battery, turn the key on, and use John Deere Service ADVISOR (or the onboard CommandCenter diagnostic menu) to clear the stored 000639.14 fault code.

8. 8

   Test

   Run the machine and test the air conditioning and heater functions to verify operation and ensure the CAN BUS fault does not return.