Case IH 520193-04 - VCM – VCM / UCM: Redundant wheel angle sensor voltage low

This fault code indicates that the signal voltage from the redundant (secondary) wheel angle sensor has dropped below the normal operating range. This typically means the sensor's signal circuit is shorted to ground (low source), there is an open circuit in the wiring, or the sensor itself has failed internally.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect series (e.g., Magnum 400)
• Case IH Steiger / Quadtrac series
• Case IH Maxxum and Puma series
• Case IH Patriot and Trident sprayers (Steer Ready)

1. 1

   Visually inspect the wheel angle sensor (WAS) located on the front axle steering cylinder or tie rod. Check the physical mounting bracket and linkage arm to ensure they haven't been bent or damaged by field debris.

2. 2

   Disconnect the sensor and inspect the pins for corrosion, moisture, or pushed-out pins.

3. 3

   Trace the wiring harness back to the VCM/UCM, looking for chafing or pinched wires that could cause a short to ground.

4. 4

   Using a multimeter or the tractor's diagnostic display, monitor the sensor voltage. A healthy wheel angle sensor typically sweeps from approximately 1.00V (full left) to 2.50V (center) to 4.00V (full right). If the voltage is stuck near 0V regardless of wheel position, the circuit is shorted low or the sensor is dead.

1. 1

   Preparation

   Park the machine on a level surface, center the steering wheels, turn off the engine, and disconnect the battery power.

2. 2

   Disconnect sensor

   Disconnect the electrical connector from the faulty wheel angle sensor.

3. 3

   Remove linkage arm

   Remove the retaining hardware (usually M8 bolts/nuts) connecting the sensor linkage arm to the axle tie rod bracket.

4. 4

   Remove sensor

   Unbolt the sensor body from its mounting bracket and remove the unit.

5. 5

   Install new sensor

   Mount the new wheel angle sensor to the bracket. Reattach the linkage arm, ensuring you use the correct arm length (some kits include both a short arm for standard axles and a long arm for specific heavy-duty axles).

6. 6

   Reconnect harness

   Reconnect the electrical harness to the sensor.

7. 7

   Perform steering calibration

   Power on the machine. You MUST perform a steering calibration via the Pro 1200 or Viper 4+ display for the VCM to learn the new sensor's parameters. Drive the machine at a slow speed (1-4 MPH). Turn the steering wheel full left until the sensor voltage reads approx 1.00V, and set the 'Left' value. Turn the steering wheel to the right until the wheels are perfectly straight (approx 2.50V) and set the 'Center' value. Turn the steering wheel full right (approx 4.00V) and set the 'Right' value.

8. 8

   Clear codes and test

   Clear the fault codes and test the auto-guidance system to ensure steering tracks are aligned.