Case IH 15261 - AST – AST (Advanced Steering / Auto Steer) Module: Cut-off solenoid stuck closed. Spool movement test at transition from on-road to off-road failed.

When the tractor transitions from 'on-road' mode to 'off-road' mode, the steering controller performs a mandatory diagnostic off-road safety check on the cut-off valve. This test verifies that the spool inside the cut-off solenoid can move freely. Code 15261 indicates that the spool movement test failed because the cut-off solenoid is physically or hydraulically stuck in the closed position. As a safety precaution, the controller will de-energize the valve, enter a safe state, and disable electro-hydraulic steering (auto-guidance).

• MAXXUM T4E
• VESTRUM CVX
• Case IH Maxxum series
• Case IH Puma series
• Case IH Optum series
• Case IH Magnum / Steiger series

1. 1

   Check hydraulic flow to ensure the steering valve is being supplied with sufficient hydraulic oil.

2. 2

   Bleed all air from the steering system by turning the steering wheel fully left, then fully right, a minimum of 10 times. Listen for abnormal noise or vibration.

3. 3

   Inspect the wiring harness and connector at the cut-off solenoid on the steering valve for corrosion, pushed pins, or wire chafing.

4. 4

   Ensure the tractor is parked on an 'on-road' surface (unpainted concrete or asphalt) if attempting a calibration routine.

1. 1

   Relieve Pressure

   Park the tractor on a flat surface, turn off the engine, and actuate the steering wheel to relieve residual hydraulic pressure.

2. 2

   Locate the Steering Valve

   Locate the main electro-hydraulic steering valve assembly (usually located under the cab or near the front bulkhead).

3. 3

   Inspect the Cut-Off Solenoid

   Locate the specific cut-off solenoid on the valve block. Remove the solenoid coil and check for signs of overheating or cracking.

4. 4

   Remove and Clean the Valve Spool

   Carefully extract the cut-off solenoid valve cartridge. Inspect the spool and the valve bore for metal debris, contamination, or scoring that would cause it to stick closed. Clean the spool with brake cleaner and hydraulic fluid.

5. 5

   Test Spool Movement

   Verify that the spool moves freely against its internal spring. If it binds, the cartridge must be replaced.

6. 6

   Reinstall / Replace

   Install the cleaned or new cut-off solenoid valve cartridge and torque to OEM specifications. Reattach the electrical connector.

7. 7

   Bleed and Test

   Top off the hydraulic fluid (Case IH Hy-Tran). Start the engine and perform the lock-to-lock steering procedure (10 times) to bleed the system.

8. 8

   Clear Codes

   Use the A-post display or a diagnostic tool to clear the AST fault codes, then cycle the tractor from on-road to off-road mode to verify the spool movement test passes.