Case IH 15256 - AST – AST (Advanced Steering / Auto Guidance) control subsystem: Incorrect steering valve controller configuration - Configured for incorrect steering valve type.

This code indicates a software-to-hardware mismatch. The electronic controller managing the autoguidance/steering system has been programmed for a specific type of electro-hydraulic steering valve, but it is detecting or expecting a different physical valve type. This typically happens after a module replacement, a software update, or a loss of memory configuration.

• MAXXUM T4E
• VESTRUM CVX
• Farmall series (e.g., 40, 45, 50, 115C, 115U)
• Optum
• Steiger
• Puma
• Maxxum series
• Mid-Range Common Cab Combines
• Flagship Combines

1. 1

   Verify recent service history to see if the AST controller, Nav Controller, or steering valve was recently replaced, or if a software flash wiped the configuration.

2. 2

   Inspect the physical steering valve installed on the machine to confirm its exact type and part number.

3. 3

   Access the ISObus, Pro 700, Pro 1200 display, or instrument cluster diagnostic menus to view the currently selected steering valve type in the AST controller.

1. 1

   Access AST Configuration Menu

   Via Instrument Cluster (navigate 'H' menus to R1 module, menu H3, select AST) or via Pro 700 / Pro 1200 Display (go to ISObus diagnostic page or Toolbox > Drive/Nav settings).

2. 2

   Correct Valve Type

   Locate the steering valve configuration setting and change the selected valve type to match the physical hardware installed on the machine. Save the configuration.

3. 3

   Warm Up System

   Ensure the hydraulic oil is at normal operating temperature before proceeding to calibration.

4. 4

   Perform Steering Calibrations

   Drive the vehicle to a wide-open area. Navigate to the Calibration menu and execute the Steering Valve Calibration so the machine can test spool movement and acquire new parameters.

5. 5

   Perform Secondary Calibrations

   Run a Roll Calibration and a Rear Wheel Position Calibration if required to ensure the AccuGuide system is fully zeroed out.

6. 6

   Clear Codes and Test

   Cycle the key, clear the inactive 15256 fault code, and engage the autoguidance system in the field to verify proper operation.