John Deere 000639.14 – AIC, TSA, VCU, TEC, XMA, DSM, ATC: Vehicle CAN BUS Fault Involving Cab Module or Arm Rest Module

A communication problem has been detected on the Vehicle Controller Area Network (CAN) bus, specifically related to the Cab Module or Armrest Interface Control Unit (AIC). The controller has detected a high rate of errors in the messages it is receiving, exceeded its error limit, or entered a 'Bus Off' state where it has stopped transmitting due to excessive errors. This interrupts the flow of critical operational data between modules.

• 8225R
• 8245R
• 8270R
• 8295R
• 8320R
• 8335R
• 8345R
• 8370R
• 8400R
• 8310RT
• 8335RT
• 8360RT
• 9470RT
• 9520RT
• 9570RT
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 7230
• 6120
• 6220
• 6320
• 6420
• 6120L
• 6220L
• 6320L
• 6420L
• 6520L
• 744K Series II 4WD Loaders
• Combines (GS3 Command Center)

1. 1

   Use the machine's display (e.g., CommandCenter) to view all active and stored diagnostic trouble codes, noting all controllers logging 000639.14 or other communication codes

2. 2

   Attempt simple resets: restart the machine, reduce electrical load, or increase engine RPM to see if a voltage-related issue clears. Also try disconnecting the battery for three minutes to clear a memory issue after a significant temperature change

3. 3

   Check CAN Bus error counts in the diagnostics menu for 'BUS Off', 'BUS Warn', or 'Passive' errors (increasing counts indicate an ongoing problem)

4. 4

   Visually inspect the CAN bus harness and connectors for the affected modules (Armrest, Cab, etc.) for abrasion, pinching, or corrosion. Wiggle the harness while observing error counts or voltage

5. 5

   Perform a CAN Bus resistance test with battery disconnected: measure resistance between CAN High and CAN Low (pins C and D on the 9-pin diagnostic connector). ~60 Ohms is normal, ~120 Ohms indicates one missing terminating resistor, and Open Loop (OL) indicates both are missing or a wiring break

6. 6

   Check CAN Bus voltages with key on/engine off: CAN High (yellow wire) and CAN Low (green wire) should both measure approximately 2.5V relative to ground. Significant deviation from these voltages can point to a faulty controller or a short in the wiring

1. 1

   Address other active codes

   If other specific sensor or circuit fault codes are active, diagnose and repair those first, as they can sometimes cause general CAN bus errors.

2. 2

   Isolate the faulty component

   If resistance or voltage checks are abnormal, unplug controllers from the Vehicle CAN bus one at a time. Re-check bus resistance and voltages after each to isolate the faulty module or harness section.

3. 3

   Swap terminating resistors

   Swap the two terminating resistors on the vehicle CAN bus. If the problem resolves or changes, replace the faulty resistor.

4. 4

   Repair harness issues

   If the wiggle test or visual inspection revealed wiring damage, repair the affected section, such as fixing a chafed wire or cleaning a corroded connector pin.

5. 5

   Replace faulty module

   If a specific control unit (like the AIC or VCU) is identified as bringing down the network when plugged in, replace the module.