Case IH 15206 - AST – Steering Valve Controller (SVC) / AST: Steering valve controller has detected the CAN bus offline.

The Steering Valve Controller has lost communication with the tractor's Controller Area Network (CAN bus). The controller is unable to send or receive the messages required to coordinate steering functions with the rest of the machine's systems.

• MAXXUM T4E
• VESTRUM CVX
• Farmall Series 40, 45, 50, and 115U
• AFS Connect Magnum Series 180, 200, 220, 240, 250, 280, 310, 340, and 380
• Vestrum CVX Series 100, 110, 120, and 130

1. 1

   Access On-Board Diagnostics via the instrument cluster (H menus, R1 module, menu H3, AST system) to verify subsystem status

2. 2

   Perform a CAN Bus Resistance Test at the diagnostic connector (pins C and D) with the key OFF; it should read exactly 60 ohms

3. 3

   Visually inspect the wiring harness for rubbing or chafing under the cab, and check SVC connectors for moisture, bent pins, or corrosion

4. 4

   Connect the Case IH Electronic Service Tool (EST) to verify if the AST/SVC is the only module offline

1. 1

   Isolate the Fault

   If the CAN bus resistance test fails (not 60 ohms), locate and inspect the CAN bus terminating resistors. Replace any faulty terminators.

2. 2

   Check Power and Ground

   Disconnect the harness from the Steering Valve Controller. Turn the key ON and verify that the controller is receiving proper 12v power and has a solid ground.

3. 3

   Test the Data Lines

   With the key ON, check the voltage on the CAN bus data lines at the controller connector. The yellow and green CAN wires should read approximately 2.4 to 2.5 volts.

4. 4

   Repair Wiring

   If power, ground, or CAN voltages are missing, trace the harness back to the main splice and repair any broken wires or corroded connectors.

5. 5

   Replace the Controller

   If the wiring harness is perfectly intact, voltages are correct, and the CAN bus resistance is 60 ohms, the Steering Valve Controller has suffered an internal failure and must be replaced.

6. 6

   Software Calibration

   If a new Steering Valve Controller is installed, it must be flashed and calibrated using the Case IH Electronic Service Tool (EST) to match the tractor's specific dataset.