John Deere 708.21 – Steering System Control Unit (SSU): Steering Wheel Position Sensor Channel 1, Fault

The steering control module has detected an erratic, missing, or out-of-range electrical signal from Channel 1 of the steering wheel position input device (sensor), which is critical for electronic steering and guidance systems like AutoTrac.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6145J
• 6165J
• 6180J
• 6205J
• 8100T
• 8120
• 8225R
• 8230
• 8245R
• 8260R
• 8310R
• 8320R
• 8360R
• 8430
• 8520
• 9470RT
• 9520RT
• 9570RT
• CH570
• CH670
• 3520

1. 1

   Check for concurrent codes such as 000709.xx or 001231.xx, which point heavily to a shared wiring issue or a failed sensor.

2. 2

   Visually inspect the 3-pin connector at the steering wheel position sensor for corrosion, backed-out pins, or wire chafing along the steering column harness leading to the control module.

3. 3

   Test the Sensor Supply 1 circuit from the control unit to ensure the sensor is receiving the correct reference voltage.

4. 4

   Verify the unswitched supply voltage to the Steering System Control Unit by checking related fuses (such as F23) and battery connections.

5. 5

   Use John Deere Service ADVISOR to monitor the live data for the Steering Wheel Position Sensor Channel 1, observing if the signal drops out or spikes erratically when the steering wheel is turned.

1. 1

   Disconnect Power

   Disconnect the machine's battery to prevent electrical shorts while servicing the steering control circuits.

2. 2

   Access the Sensor

   Remove the necessary steering column cowlings or access panels to reach the steering wheel position sensor (usually located on the steering column shaft or steering valve).

3. 3

   Replace the Sensor

   Disconnect the sensor's electrical connector. Unbolt and remove the faulty steering wheel position sensor. Install the new OEM sensor and secure it in place.

4. 4

   Reconnect and Reassemble

   Plug the wiring harness back into the sensor and reinstall any removed panels. Reconnect the battery.

5. 5

   Clear Codes and Calibrate

   Connect the John Deere Service ADVISOR tool. Clear the 000708.21 diagnostic trouble code.

6. 6

   Software Configuration

   You must perform the steering system calibration procedure via Service ADVISOR so the XMC/A-Box module can learn the new sensor's center and end-stop positions.

7. 7

   Test Drive

   Operate the machine and test the AutoTrac or ActiveCommand steering system to ensure the fault code does not return. (Note: If the code returns immediately and the wiring is verified good, the XMC / A-Box control unit itself may require a software reflash or physical replacement).