John Deere 709.21 – Steering System Control Unit (XMC, XSC, XMA, TMA, PSC): Steering Wheel Position Sensor Channel 2, Fault

The controller detects a signal loss, mismatch, or failure on the Channel 2 circuit of the Steering Input Device (SID). When this code is active, automated steering systems like AutoTrac are typically disabled for safety.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8225R
• 8235R
• 8245R
• 8260R
• 8285R
• 8295R
• 8310R
• 8320R
• 8335R
• 8345R
• 8360R
• 8400R
• 7200R through 7310R
• 9370R through 9620RX
• 9470RT
• 9520RT
• 9570RT
• 6145J
• 6165J
• 6180J
• 6205J
• 8100T through 9630T
• CH570
• CH670
• 3520

1. 1

   Remove the steering column cowl/covers to access the Steering Input Device (SID).

2. 2

   Locate the two steering wheel position sensor connectors at the SID.

3. 3

   Interchange (swap) the connectors for Sensor 1 and Sensor 2.

4. 4

   Clear the diagnostic trouble codes and cycle the key/steering to see which code returns. If the same DTC (Channel 2) returns, the issue is in the wiring harness between the SID and the Steering Control Unit. If the DTC shifts to the other channel (Channel 1), the sensor inside the Steering Input Device has failed internally.

5. 5

   Check for software updates: Verify the XMC/BCU is flashed with the latest software via the John Deere Custom Performance program, as communication or software glitches can sometimes cause this fault.

1. 1

   Access the Components

   Power down the machine and remove the plastic covers surrounding the steering column to expose the Steering Input Device (SID) and wiring harness.

2. 2

   Harness Inspection & Repair

   If the diagnostic swap test pointed to the harness, inspect the wiring (e.g., harness AL207316) for chafing, pinched wires, or corroded pins at both the sensor connector and the XMC module connector. Repair or replace the harness as needed.

3. 3

   Sensor/SID Replacement

   If the diagnostic swap test pointed to the sensor, remove the faulty Steering Wheel Position Sensor or the entire Steering Input Device assembly (depending on whether your specific model services the sensor separately or as a complete SID/Brake module).

4. 4

   Reassembly

   Install the new sensor/SID and reconnect the wiring harness in its original (un-swapped) configuration. Reinstall the steering column covers.

5. 5

   Calibration

   Connect a diagnostic service tool to clear the stored 000709.21 fault code. Perform a steering wheel angle calibration procedure as required by the XMC controller to sync the new sensor.