Case IH 520204-28 - VCM – VCM / UCM: Steering valve controller spool out of neutral at power-up

The electrohydraulic (EH) main spool inside the steering valve is detected as not being in its neutral (centered) position when the controller powers up. This triggers a severe Safety Fault Detection Algorithm to prevent unintended steering movements or 'runaway' steering when the tractor is started.

• MAGNUM AFS Connect
• Magnum AFS Connect series
• Magnum 400
• Steiger series
• Puma series

1. 1

   Check system voltage during engine cranking (must not drop below 9V to avoid false faults)

2. 2

   Bleed the steering system to ensure no air in the hydraulic lines is causing the spool to stick or drift

3. 3

   Inspect external sensors (Wheel Angle Sensor and SASA) to ensure they are not detached, loose, or out of adjustment

4. 4

   Check hydraulic shock (chock) valves to verify they have not been forced open or are leaking

5. 5

   Verify parameter setup to ensure sensor parameters and wheel angle calibrations have not been corrupted

1. 1

   Hydraulic Purge

   Start the tractor and perform the lock-to-lock steering procedure (10 times) to purge air. Shut the tractor down, wait for the modules to power down completely, and restart to see if the power-up fault clears.

2. 2

   Sensor Calibration

   If the fault persists, move the tractor to an on-road surface (unpainted concrete or asphalt). Use the Case IH diagnostic tool (or Danfoss PLUS+1 service tool) to recalibrate the Wheel Angle Sensor (WAS) and the steering valve parameters.

3. 3

   Inspect Linkages

   Physically inspect the mechanical linkages for the WAS. If the vehicle geometry has changed (e.g., bent tie rod), the system may think the spool is out of control.

4. 4

   Valve Replacement

   If the voltage is stable, sensors are intact, and calibration fails, the EH main spool is likely physically sticking or the internal LVDT position sensor has failed. The steering valve and/or the attached PVED-CLS controller must be replaced.