Case IH 15265 - AST – AST (Advanced Steering / Auto Guidance) Steering Valve Controller: Steering valve controller failure - Overvoltage supervisor self-test failed.

This code indicates an internal hardware or software failure within the steering controller. Specifically, the internal safety monitoring circuit (the "supervisor" responsible for detecting overvoltage conditions to protect the module) failed its automated self-test during initialization or operation.

• MAXXUM T4E
• VESTRUM CVX
• Puma Series (140, 150, 165, 180, 195, 210, 225)
• Maxxum Series (115, 125, 135, 140, 150)
• Magnum Series AFS Connect (250, 280, 310, 340, 380)
• Optum Series
• Vestrum CVX Series
• Farmall Series (40, 45, 50)

1. 1

   Test the main power supply and ground circuits at the steering valve controller harness. Ensure the tractor's alternator is not overcharging and that voltage is stable (typically 12V-14V) without spikes.

2. 2

   Inspect the wiring harness and connectors at the AST steering valve controller for corrosion, water ingress, or damaged pins that could cause a short to power.

3. 3

   Clear the fault code using the EST (Electronic Service Tool) or the H-menu on the instrument cluster. Cycle the key to see if the self-test passes on the next power-up.

4. 4

   If the voltage supply is clean and the code returns immediately upon key-on, the steering valve controller has suffered an internal hardware failure and must be replaced.

1. 1

   Park and secure the tractor

   Park the tractor on a level surface, turn off the engine, engage the parking brake, and remove the key.

2. 2

   Locate the controller

   Locate the AST steering valve controller (typically mounted directly to the hydraulic steering orbital valve/block under the cab or near the front firewall).

3. 3

   Clean the area

   Thoroughly clean the area around the valve to prevent dirt from entering the hydraulic system.

4. 4

   Disconnect harness

   Disconnect the electrical harness from the steering valve controller.

5. 5

   Remove faulty controller

   Unbolt and remove the faulty steering valve controller / steering valve assembly. (Note: Depending on the exact model, the controller may be integrated into the electro-hydraulic steering valve block, requiring the hydraulic lines to be capped and the whole block replaced).

6. 6

   Install new controller

   Install the new steering valve controller/assembly and torque mounting bolts to OEM specifications.

7. 7

   Reconnect harness

   Reconnect the electrical harness.

8. 8

   Perform calibration

   Crucial Final Step: Perform the AST steering calibration procedure. This must be done using the dealer EST diagnostic tool or by navigating the H-menus on the instrument cluster (e.g., navigating to the R1 module, menu H3, and selecting the AST system to initiate calibration).