John Deere 000084.09 – SSU: CAN Bus Wheel Speed Message Missing

The Steering System Control Unit (SSU) is not receiving the expected wheel speed or ground speed data from the vehicle's CAN bus network. This indicates an interruption in the data stream, potentially related to the Front Chassis Module or transmission controller, preventing the SSU from obtaining necessary speed information.

• 7720
• 7820
• 7920
• 7630
• 7730
• 7830
• 7930
• 8130
• 8230
• 8330
• 8430
• 8530
• 9230
• 9330
• 9430
• 9530
• 9630
• 7810
• 4930

1. 1

   Restart the vehicle to see if the fault is a temporary communication glitch

2. 2

   Review the diagnostic trouble code history for other active codes, particularly those related to the SSU or transmission (PTI/PTP/PTQ)

3. 3

   Check relevant fuses, such as F23 for the SSU, and F6 or F35 for the transmission controller (on PowrQuad Plus or IVT models)

4. 4

   Visually inspect wiring harnesses and connectors associated with the SSU, wheel speed sensors, and transmission controller for damage, corrosion, or loose connections

5. 5

   Inspect the area around the batteries and alternator for visible damage or debris

1. 1

   Identify speed signal source

   Determine if the wheel speed message originates from the transmission controller (e.g., PowrQuad Plus) or a dedicated wheel speed sensor.

2. 2

   Perform CAN bus diagnostics

   Use a CAN bus analyzer to monitor network traffic. Check for proper CAN bus voltages (typically around 2.5 volts on CAN high and low) and verify terminating resistor integrity (60 ohms between CAN high and low wires).

3. 3

   Test speed signal components

   Test the dedicated wheel speed sensor for proper output, or diagnose the transmission control unit and its related sensors if the signal originates there.

4. 4

   Inspect and test wiring harness

   Perform continuity and load tests on the wiring harness between the signal source and the SSU to identify any breaks or high-resistance points.

5. 5

   Diagnose and replace SSU

   If all other components, sensors, and wiring are functioning correctly, the Steering System Control Unit (SSU) itself may be faulty and require replacement.