John Deere 523826.14 – SSU (Steering System Unit) or XSC (Steering Control): No Movement Of Front Axle When Turn Was Requested / B139 Steering Angle Sensor Recognizes No Movement

This diagnostic trouble code (DTC) is generated when the Wheel Angle Sensor (WAS) does not detect any physical steering movement at the front wheels, despite the steering wheel position sensor (B138) transmitting steering commands to the control unit. This indicates a discrepancy between the operator's steering wheel input and the actual steering motion of the axle.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 7R Series
• 8R Series
• 9230
• 9330
• 9430
• 9530
• 9630
• 6020 Series (6120-6420)
• 7630
• 7730
• 7830
• 7930
• 7810
• 4930
• 4940
• R4030
• R4038
• R4044
• R4045
• R4060
• S-Series Combines
• 8000 Series Forage Harvesters
• 9000 Series Forage Harvesters

1. 1

   Inspect the Wheel Angle Sensor (WAS) on the front axle for proper mounting, physical damage, and secure connections.

2. 2

   Verify sensor signals using a diagnostic tool to monitor live data from the WAS and Steering Wheel Position Sensor (B138) for consistency and expected range, ensuring the WAS ADC values change when the wheels are manually moved.

3. 3

   Check for mechanical issues in the steering mechanism (tie rods, cylinders, linkages) for looseness, wear, or mechanical play.

4. 4

   Inspect wiring harnesses leading to the WAS and steering control valves for damage, corrosion, or open circuits.

5. 5

   Verify steering control valves are receiving commands and are free from hydraulic blockages or mechanical binding.

1. 1

   Address Mechanical Play

   Tighten or replace any worn mechanical steering components (tie rods, pins, bushings) that are causing physical slop in the steering axle.

2. 2

   Repair Wiring

   If diagnostic checks reveal an open circuit or short, repair or replace the damaged section of the wiring harness leading to the WAS or B138 sensor.

3. 3

   Replace Faulty Sensors

   If the wiring is intact but the Wheel Angle Sensor or Steering Wheel Position Sensor is outputting erratic, out-of-range, or dead signals, replace the defective sensor with a genuine OEM part.

4. 4

   Recalibrate the System

   After replacing the WAS or addressing mechanical issues, you must recalibrate the steering system and Wheel Angle Sensor using John Deere diagnostic software.

5. 5

   Update SSU Software

   Check for and install any available firmware updates for the SSU control software to address known signal processing bugs or sensor synchronization issues.

6. 6

   Clear and Test

   Restart the vehicle, clear the codes, and test the steering lock-to-lock to ensure the fault does not return.