Case IH 520200-22 - VCM – VCM / UCM: Loss of communication between the steering valve controller and the vehicle speed sensor

The steering controller is no longer receiving the necessary speed data over the CAN bus to safely modulate steering sensitivity and auto-guidance functions.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series (180, 200, 220, 240, 250, 280, 310, 340, 380, 400)

1. 1

   Check the vehicle parameter settings in the display (e.g., tire size, gear ratio) for abnormal settings causing speed calculation mismatches.

2. 2

   Inspect the physical installation state of the vehicle speed sensor, ensuring the sensor gap is correct and it has not backed out or become loose.

3. 3

   Inspect the wiring harness between the vehicle speed sensor, the transmission output, and the steering valve controller for open circuits, shorts to ground, or CAN bus offline errors.

1. 1

   Verify Parameters

   Access the diagnostic menu and confirm that the parameter settings (tire size/gear ratio) are correct. If not, reset the parameters to normal.

2. 2

   Inspect the Sensor

   Locate the vehicle speed sensor (typically reading the rpm speed at the ranges box output/clutches output). Check its mounting. If the installation is abnormal or the gap is incorrect, reinstall and properly gap the sensor.

3. 3

   Test the Wiring

   Disconnect the sensor and use a multimeter to check for continuity and proper voltage on the CAN/signal lines back to the VCM/UCM. Repair any damaged wiring or corroded connectors.

4. 4

   Replace the Sensor

   If the wiring is intact, the parameters are correct, and the sensor is properly installed but the code persists, the vehicle speed sensor has failed internally and must be replaced.

5. 5

   Clear Codes

   After replacement, cycle the key, test drive the tractor to ensure speed data is registering, and clear the fault codes.