John Deere 001231.12 – RLC, TEC, TEI, VCU, CCU: ISO BUS CAN BUS Fault

A communication failure has been detected on the CAN (Controller Area Network) bus, specifically related to the Cab Roof Module (RLC). The .12 Failure Mode Identifier (FMI) indicates a 'bad intelligent device or component,' meaning the RLC is either the source of the communication problem or has lost communication with another critical controller on the network. This breakdown can cause erratic behavior in systems controlled by the RLC, such as lights and wipers, or disrupt other machine functions relying on CAN bus data.

• 9330
• 9430
• 9530
• 9630
• 6145J
• 6165J
• 6180J
• 6205J
• 6120
• 6220
• 6320
• 6420
• 6120L
• 6220L
• 6320L
• 6420L
• 6520L
• 7-Series Tractors
• 8-Series Tractors
• 9-Series Tractors
• 370E
• 410E
• 460E
• 724L

1. 1

   Power cycle the system by turning off main power, waiting 30-60 seconds to allow modules to discharge, and restarting the machine to clear intermittent issues

2. 2

   Check for other active fault codes, particularly those related to low voltage or sensor failures that could disrupt communication

3. 3

   Verify power and ground supplies to the RLC and other ECUs, ensuring battery voltage is stable and above 12 volts

4. 4

   Inspect all ISOBUS and CAN bus physical connections, including the main 9-pin rear connector and RLC connectors, for dirt, moisture, corrosion, or bent pins

5. 5

   Check CAN bus voltage with the key on (CAN High should be slightly above 2.5V, CAN Low slightly below 2.5V, totaling approximately 5V)

6. 6

   Measure CAN bus resistance with power off (should be approximately 60 ohms, indicating both 120-ohm terminating resistors are intact)

1. 1

   Address basic connection issues

   Clean any dirty or corroded connectors found during inspection and secure all loose connections. Rectify any low voltage conditions.

2. 2

   Isolate the faulty component

   Disconnect other controllers from the CAN bus one by one (e.g., implements, GPS receiver) to see if the fault code clears. This helps determine if a specific device is causing excessive bus traffic or errors.

3. 3

   Inspect wiring harness

   Examine the wiring harness in the cab roof area for chafing, pinching, rodent damage, or shorts between CAN wires or to power/ground.

4. 4

   Update software and configuration

   Check for available software updates for the display and controllers. On the virtual terminal (VT), try deleting object pools or implement profiles and reconnecting the implement to reload its software.

5. 5

   Replace the RLC or faulty controller

   If all wiring and connections are good and the fault consistently points to the RLC, replace the module. Note that replacement controllers often require programming by a certified dealer.