Case IH 15252 - AST – AST (Auto Steering / Advanced Steering) Control Subsystem / Steering Valve Controller: Roading switch stuck closed

The Roading Switch (or Master Roading Switch) is a safety toggle used to completely disable the tractor's auto-guidance and automated steering systems when driving on public roads. This fault code triggers when the controller detects that the switch circuit is continuously closed (stuck in the 'On-Road' position). This prevents the auto-guidance system from engaging because the system believes the tractor is on a public road or there is a short circuit in the wiring.

• MAXXUM T4E
• VESTRUM CVX
• Steiger Series (335, 385, 435, 485, 535, 620)
• Magnum Series (220, 310, 340)
• Puma Series (165, 180, 195, 210, 225)
• Farmall CVT Models

1. 1

   Physically check the Master Roading Switch to ensure it is not jammed or sticky

2. 2

   Manually toggle the switch back and forth between the 'Road' and 'Field' positions to see if stuck contacts clear

3. 3

   Check for associated codes like 15253, 15254, or U219 which point to harness failures or CAN communication errors

4. 4

   Inspect the wiring harness and switch connector (e.g., Connector C656M) for pinched wires or shorts to ground

1. 1

   Power Down

   Turn off the tractor, remove the key, and ensure all hydraulic pressure is relieved before servicing electrical components near the steering valves.

2. 2

   Access the Switch

   Remove the trim panel on the headliner or upper console to access the back of the Auto Guidance Roading Switch.

3. 3

   Disconnect and Test

   Disconnect the wiring harness from the switch. Use a digital multimeter to test the switch for continuity.

4. 4

   Evaluate the Switch

   Toggle the switch. If the multimeter shows continuity (a closed circuit) regardless of the switch position, the internal contacts have failed and the switch must be replaced.

5. 5

   Test the Harness

   If the switch tests normally (opens and closes properly), the fault lies in the wiring. Test the harness pins for a short to voltage or short to ground between the switch connector and the AST Steering Controller. Repair any damaged wiring.

6. 6

   Reassembly and Clearing

   Install the new switch or repaired harness. Power the tractor on, navigate to the ISOBUS diagnostic page or AST system menu on the instrument cluster, and verify that the switch state now registers correctly and the fault code is inactive.