Case IH 15243 - AST – AST / Steering Valve Controller: Steering control message (from TCU/UCM) invalid data value

A CAN bus communication issue where the steering valve controller (part of the Auto Guidance/AST system) is receiving a message from the Transmission Control Unit (TCU) or Universal Control Module (UCM), but the data payload within that message is invalid, corrupted, or out of the expected range.

• MAXXUM T4E
• VESTRUM CVX
• Puma Series
• Magnum Series
• Optum Series
• Maxxum Series
• Farmall Series

1. 1

   Use a diagnostic tool to verify CAN bus communication between the AST/Steering controller and the UCM/TCU, checking for offline codes (15240, 15241, 15242)

2. 2

   Check the current software version of the UCM and TCU for outdated software

3. 3

   Inspect the CAN bus wiring harness between the UCM/TCU and the steering valve controller for chafing, corrosion, or loose connector pins

4. 4

   Verify the steering valve controller configuration, checking for related configuration error codes (15244-15247)

1. 1

   Connect Diagnostic Equipment

   Plug into the machine's diagnostic port and pull all active and stored codes from the AST, UCM, and TCU.

2. 2

   Inspect and Repair Wiring

   If physical damage or high resistance is found in the CAN lines connecting the steering controller to the UCM, repair the wiring harness or replace the damaged connector pins.

3. 3

   Update Module Software

   Flash the UCM and TCU with the latest CNH software releases (e.g., updating the UCM to software version 16.2.0.0 or the TCU to version 1.8.0.0, depending on the specific tractor model).

4. 4

   Recalibrate the Steering System

   Perform a steering system calibration via the AST menu on the instrument cluster or diagnostic tool to rewrite the correct configuration data to the steering valve controller.

5. 5

   Module Replacement

   If the wiring is intact, software is up to date, and the UCM or steering controller still outputs or receives corrupted data due to an internal hardware failure, replace the faulty module.