John Deere 000639.12 – BCU / TEC / ICU: CAN Bus Fault: Arm Rest Module

A communication failure has been detected on the vehicle's Controller Area Network (CAN bus) specifically related to the Arm Rest Module (CSM). This fault is triggered when a primary control unit, such as the Basic Control Unit (BCU) or Tractor Electronic Control Unit (TEC), detects a high error rate in messages from the Arm Rest Module or a complete loss of communication, often manifesting as a 'message missing' or 'message overflow' error.

• 7R Series
• 8R Series
• 8225R
• 8245R
• 8270R
• 8295R
• 8320R
• 8345R
• 8370R
• 8400R
• 9330
• 9430
• 9530
• 9630
• 9560
• 9660
• 9670 STS
• 9770 STS
• 7760
• Z370R

1. 1

   Record and clear fault codes using the machine's display, then restart the machine to determine if the fault is intermittent or persistent

2. 2

   Visually inspect the wiring harnesses and connectors associated with the Arm Rest Module for chafing, corrosion, pinched wires, or loose connections

3. 3

   Verify that the Arm Rest Module is receiving the correct supply voltage and has a solid ground connection

4. 4

   Perform a CAN Bus Integrity Check (Power Off): Measure resistance between CAN High and CAN Low wires (should be approximately 60 Ohms; 120 Ohms indicates a missing terminating resistor/open circuit, while significantly lower indicates a short)

5. 5

   Perform a CAN Bus Voltage Check (Power On, engine off): Measure DC voltage between CAN High and ground (expected 2.5 to 3.0 volts) and CAN Low and ground (expected 2.0 to 2.5 volts)

1. 1

   Isolate the fault

   If initial checks point to a wiring issue, use machine-specific wiring diagrams to trace the CAN bus wiring to and from the Arm Rest Module. Disconnect other control units on the same circuit to isolate the source of the problem.

2. 2

   Test Arm Rest Module

   Test the Arm Rest Module by substituting it with a known good unit, if available.

3. 3

   Repair or replace wiring

   If a damaged section of the wiring harness is found, repair it according to industry best practices or replace the entire harness.

4. 4

   Replace faulty module

   If the Arm Rest Module is determined to be faulty after testing, replace the unit.

5. 5

   Reprogram replacement module

   Program the new control module using John Deere's Service ADVISOR software to ensure it functions correctly with the specific machine.