Case IH 520192-03 - UCM – UCM: Primary wheel angle sensor voltage high.

The analog wheel angle sensor connected to the AD1 input is detecting a voltage that is above the normal operating range. This indicates a short-circuit to a high voltage source (VCC or battery) on the signal wire, or an internal failure of the sensor itself.

• MAGNUM AFS Connect
• Maxxum
• Puma
• Magnum
• Steiger
• Axial-Flow 7120
• Axial-Flow 8010
• Axial-Flow 9230
• Patriot 3230
• Patriot 3320
• Patriot 3330
• Patriot 4420
• Patriot 4430

1. 1

   Check the wire connected to the AD1 input on the steering controller for a short circuit to a high voltage source (VCC or 12V battery).

2. 2

   Check the primary wheel angle sensor for internal failure.

3. 3

   Verify the sensor's mechanical linkage and mounting integrity, as physical damage can sometimes force the sensor past its internal voltage stops.

1. 1

   Turn off vehicle

   Always shut off the vehicle when working around the wheel angle sensor. The steering mechanism could move suddenly and cause severe injury if the system is active.

2. 2

   Disconnect and inspect sensor

   Locate the primary wheel angle sensor (typically on the steering axle or steering cylinder). Disconnect the sensor harness and inspect the connector pins for corrosion, moisture, or bent pins.

3. 3

   Test the harness

   Using a multimeter, test the signal wire (AD1) on the machine-side harness for a short circuit to VCC (5V reference) or battery voltage (12V).

4. 4

   Repair wiring

   If a short circuit to power is found in the wiring, trace the harness back to the UCM/Steering Controller and repair or replace the damaged section.

5. 5

   Replace the sensor

   If the wiring tests normal (no short to power), the fault is an internal failure of the wheel angle sensor. Remove the mechanical linkage arms and replace the sensor.

6. 6

   Recalibrate sensor

   After repairing the wiring or replacing the sensor, you must perform a wheel angle sensor calibration via the in-cab display (e.g., Pro 700 / Pro 1200). Failure to calibrate the new sensor will result in signal crosscheck faults and the auto-guidance system will remain disabled.