John Deere 959.09 – CCU (Chassis Control Unit) / SCC (Rear Chassis Controller): Vehicle CAN BUS Fault Rear Chassis (CCU)

A critical communication breakdown on the vehicle's CAN bus isolating the Rear Chassis Control Unit (CCU). The system has detected that the error limit has been exceeded due to an open circuit, a short circuit, a bad ground, or excessive corrupted traffic on the CAN bus, causing the module to drop off the network.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6150R
• 8245R through 8400R
• 8310RT
• 9470RT
• 9520RT
• 9570RT

1. 1

   Pull active codes and check the count on the diagnostic monitor. Look for toggling active/inactive states, which indicates an intermittent physical connection rather than a failed module.

2. 2

   Perform a CAN Bus voltage test using a multimeter or CAN Communication Health Wizard app to read CAN High and CAN Low voltages. Look for erratic voltage spikes when wiggling the wiring harnesses.

3. 3

   Inspect the ground connections, specifically looking for a broken or loose ground wire eyelet near the battery box (Wire #0330A), which is a highly documented cause for this fault.

4. 4

   Check for power and ground at the rear SCV connectors. If absent, trace back to the frame connectors just behind the cab and inspect for corrosion or moisture intrusion.

5. 5

   Perform a continuity test from the frame connector to the middle connector of the Rear Chassis Controller (CCU) to confirm if there is a break in the chassis harness.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the main battery cables to prevent shorting during the repair.

2. 2

   Locate the Break

   Trace the ground wire (Wire #0330A) from the battery to the chassis ground point, or locate the broken wire in the rear chassis harness leading to the CCU middle connector.

3. 3

   Strip and Prep

   Cut away the damaged or corroded section of the wire. Strip back the insulation to expose clean, unoxidized copper.

4. 4

   Install New Terminal

   Crimp a new, heavy-duty eyelet terminal onto the wire.

5. 5

   Weatherproof the Connection

   Apply marine-grade, adhesive-lined heat shrink tubing over the crimp to prevent future moisture ingress and corrosion.

6. 6

   Reattach and Secure

   Bolt the ground eyelet securely to the chassis/terminal. If the break was internal to the harness, run a new bypass wire from the controller to the frame connector and secure it with zip ties.

7. 7

   Clear and Test

   Reconnect the battery, clear the stored CCU fault codes via the cab monitor, and test drive the tractor to ensure transmission shifting and SCV functions have returned to normal.