John Deere 000639.12 – TEC, TEI: Vehicle CAN BUS Fault Main Control Module (CCU)

A communication fault has been detected on the vehicle's Controller Area Network (CAN) bus, indicating that the Tractor Electronic Control Unit (TEC) or Main Control Module (CCU) is not receiving expected messages from other control modules. This communication issue within the control module can lead to reduced functionality or the non-operation of certain vehicle systems.

• 9330
• 9430
• 9530
• 9630
• 9R
• 9RX
• 8130
• 8230
• 8330
• 8430
• 8530
• 4730
• 4830
• 4930
• 4940

1. 1

   Restart the engine to see if the fault clears (Initial Reset)

2. 2

   Review the CommandCenter for any other active fault codes that may point to a more specific issue

3. 3

   Carefully inspect the wiring harnesses and connectors associated with the CAN bus system for any visible damage, corrosion, or loose connections

4. 4

   With vehicle power off, use a multimeter to measure resistance between the CAN High and CAN Low wires (should be approximately 60 ohms; a reading of 120 ohms indicates a missing terminating resistor or open circuit)

5. 5

   With power on, check the voltage of the CAN lines (CAN High should be 2.5-3.0 volts, CAN Low should be 2.0-2.5 volts; abnormal voltages indicate a short to power or ground)

6. 6

   If resistance and voltage checks are abnormal, isolate the faulty module by unplugging control units one by one and re-checking the CAN bus readings

1. 1

   Repair wiring and connectors

   If any damaged wires or corroded connectors are found during the visual inspection, repair or replace them as necessary. Ensure all connections are clean and secure.

2. 2

   Correct termination issues

   If the resistance check indicates a problem with the terminating resistors (a reading other than 60 ohms), locate and replace the faulty resistor or correct the open circuit.

3. 3

   Isolate and test modules

   If the bus is shorted or showing incorrect voltages, unplug modules on the CAN network one at a time. After unplugging each module, re-check the bus resistance and voltage. If the readings return to normal after unplugging a specific module, that module is likely the cause of the fault.

4. 4

   Replace faulty module

   If a specific control unit is identified as the source of the problem (such as the Tractor Electronic Control unit), replace it.

5. 5

   Clear codes and retest

   After performing repairs, clear all fault codes and operate the machine to ensure the issue is resolved. If the code returns, further in-depth diagnostics with specialized tools or a dealer may be required.