John Deere CAB1544 – ACU: Missing CAN Message from ACU

A primary control unit has lost communication with the Armrest Control Unit (ACU) over the CAN bus, specifically missing the status report of the multifunction lever switch. This is a communication error that can be caused by wiring problems, poor power or ground connections, or a faulty control unit such as the ACU or the Cab Power Module (CPM).

• 9470 STS
• 9540
• 9560
• 9580
• 9560 STS
• 9570 STS
• 9640
• 9660
• 9680
• 9650 STS
• 9660 STS
• 9670 STS
• 9750 STS
• 9760 STS
• 9770 STS
• 9860 STS
• 9870 STS
• 9880 STS
• CTS Series Combines
• WTS Series Combines
• S-Series Combines
• S560
• S690
• T-Series Combines
• T550
• T560
• T660
• T670
• W-Series Combines
• W540
• W550
• W650
• W660

1. 1

   Inspect wiring harnesses connected to the Armrest Control Unit and the multifunction lever for chafing, corrosion, or rodent damage

2. 2

   Check for loose connections at the Armrest Control Unit

3. 3

   Verify proper voltage and a solid ground connection at the Armrest Control Unit

4. 4

   Check for other active fault codes that may provide additional clues to the communication failure

5. 5

   Clear fault codes and operate the machine to see if the code returns, as intermittent codes may clear by cycling the ignition

1. 1

   Access the Armrest Control Unit

   Remove panels or the armrest assembly to gain access to the Armrest Control Unit and its connectors.

2. 2

   Perform Visual Inspection

   With the ACU accessible, conduct a thorough visual inspection of all related wiring and connectors as described in the diagnostic checks.

3. 3

   Reseat Connectors

   Disconnect the main electrical connectors from the Armrest Control Unit, inspect the pins for damage or corrosion, and then securely reconnect them.

4. 4

   Test the Multifunction Lever

   Test the functionality of the multifunction lever switches. If some functions work while others do not, it may indicate a problem with the lever itself rather than the entire ACU.

5. 5

   Address Wiring Issues

   If any damaged wires are found, repair them according to standard procedures, ensuring a solid and insulated connection.

6. 6

   Component Replacement

   If wiring and connections are confirmed to be in good condition and the fault persists, replace the Multifunction Lever Handle if symptoms point to a specific lever failure. If all other possibilities have been exhausted, the Armrest Control Unit may need to be replaced.