John Deere 639.14 – CCU, ACU, TEC, ICU, GR6, DSM, ETC, BIF, PL1: Vehicle CAN BUS, Very High Error Rate / CAN Error Limit Exceeded

A control unit detects an excessively high error rate on the CAN BUS, meaning it is receiving too many incorrect/corrupted messages, or it has detected a general physical problem with the CAN BUS network (such as a short circuit, electrical interference, faulty wiring, or a failed terminating resistor). This disrupts communication between critical vehicle systems, which can lead to erratic behavior, limited gear selection, or complete system failure.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 7020 Series
• 7030 Series
• 8020 Series
• 8030 Series
• 9030 Series
• 7420
• 7720
• 7820
• 7920
• 8220
• 8420
• 9330
• 9430
• 9530
• 9630
• 9470RT
• 9520RT
• 9570RT
• 6M Series
• 6R Series
• 6090MC
• 6100MC
• 6110MC
• 6170R
• 4930 Self-Propelled Sprayer
• Articulated Dump Trucks
• StarFire GPS Receivers

1. 1

   Cycle the Power: Restart the engine/machine to verify if the code is active or intermittent.

2. 2

   Inspect Wiring and Connections: Visually inspect all CAN BUS wiring (specifically the Yellow CAN-High and Green CAN-Low wires) and connectors for signs of chafing, breaks, corrosion, or loose pins.

3. 3

   Test Terminating Resistors: With the machine powered off, use a multimeter to measure the resistance across the CAN-High and CAN-Low pins at the diagnostic port. It should read approximately 60 ohms (120 ohms indicates a bad or missing resistor; 0 ohms indicates a short).

4. 4

   Isolate Modules: Disconnect modules one by one (e.g., StarFire receiver, implement connectors, ACU). If the error rate drops and the code goes inactive after unplugging a specific module, that module (or its immediate harness) is internally shorted.

5. 5

   Check for Interference: Ensure there are no unauthorized aftermarket devices (like improper data loggers or performance tuners) spliced into the CAN bus, as these can cause high error rates.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery before repairing wiring or replacing modules.

2. 2

   Repair Wiring

   If the diagnostic checks revealed chafed or broken wires (commonly found near pivot points, cab entry points, or exposed frame rails), splice and seal the wires using OEM-approved weather-tight connectors, or replace the damaged harness section.

3. 3

   Replace Terminating Resistor

   If the resistance check failed, locate the faulty CAN bus terminator (often found at the ends of the chassis or implement harness) and plug in a new replacement.

4. 4

   Replace Faulty Module

   If isolating the modules proved that a specific control unit (like the CCU or TEC) has an internal hardware fault, unbolt the module, disconnect the harness, and install a replacement unit.

5. 5

   Software Update/Calibration

   If a control module is replaced, or if the issue is caused by a known software bug, have a John Deere dealer flash the latest firmware to the control units to ensure compatibility and network stability.

6. 6

   Clear Codes

   Reconnect the battery, power on the machine, and use a diagnostic tool or the CommandCenter display to clear the stored 000639.14 code. Test drive to ensure the code does not return.