Case IH 15254 - AST – Steering Valve Controller: Roading switch voltage outside of a valid range at power up.

In Case IH auto-guidance (AST / AccuGuide) systems, the roading switch (also known as the master roading switch or auto guidance control switch) acts as a safety lockout to disable automated steering when the tractor is in transport mode on public roads. This fault code triggers when the machine is powered up and the voltage signal from this switch falls outside the expected valid parameters. This prevents the steering valve from initializing properly and disables the auto-guidance system.

• MAXXUM T4E
• VESTRUM CVX
• Steiger
• Magnum
• Puma
• Maxxum
• Farmall

1. 1

   Manually toggle the Auto Guidance Roading Switch to ensure it is not physically stuck

2. 2

   Test the voltage at the switch during key-on/power-up to determine if the circuit is shorted to ground, shorted to power, or open

3. 3

   Inspect the wiring harness and connectors between the roading switch and the steering valve controller for chafed wires, corrosion, or loose terminal pins

4. 4

   Verify the steering valve controller configuration via the ISOBus diagnostic page or a dealer service tool to ensure it hasn't lost its configuration

1. 1

   Power Down

   Turn the key off and ensure the machine is safely parked.

2. 2

   Access the Switch

   Remove the trim or console panel necessary to access the back of the Auto Guidance Roading Switch.

3. 3

   Test the Switch

   Disconnect the switch and use a multimeter to test for proper continuity/resistance across its terminals when toggled. If the switch fails the continuity test or shows internal high resistance, replace it.

4. 4

   Test the Harness

   If the switch tests good, check the harness for continuity from the switch connector to the steering valve controller pins. Repair any broken wires or replace damaged connector pins.

5. 5

   Reassembly

   Reconnect the switch and reinstall any removed trim panels.

6. 6

   Clear and Verify

   Power up the machine. Toggle the roading switch to the "Field" or "Engaged" position. Clear the fault codes from the display and verify that code 15254 does not return and that the auto-guidance system status shows ready.