Case IH 4734 – UCM (Universal Control Module): Right Swash Plate Angle Sensor Pin B Open Or Shorted To Ground

The control module is detecting that the voltage on Pin B of the right hydrostatic pump's swash plate angle sensor is either completely missing (open circuit) or has found a direct path to ground (shorted to ground).

• skid steer
• Case TR270
• Case TV380
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)

1. 1

   Visual Inspection: Tilt the cab to access the hydrostatic drive pumps. Inspect the wiring harness leading to the right swash plate angle sensor. Look for rubbed-through wire insulation, rodent damage, or pinched wires against the chassis.

2. 2

   Connector Check: Disconnect the sensor. Inspect the pins inside the connector for corrosion, moisture, or pushed-out pins.

3. 3

   Multimeter Testing: Test Pin B on the machine-side harness for continuity back to the UCM. Test Pin B for a short to ground. Verify that the sensor is receiving the correct 5V reference supply and ground from the UCM on its other pins.

4. 4

   Fluid Temperature Note: Ensure the machine is warmed up, as extremely cold and thick hydraulic fluid can cause sluggish swash plate movement, though a hard 4734 code will usually require electrical repair or sensor replacement.

1. 1

   Prepare machine

   Park the machine on a level surface, lower the loader arms completely (or engage the safety strut if they must be raised), and turn off the engine.

2. 2

   Depressurize and disconnect battery

   Relieve hydraulic tank pressure and disconnect the negative battery cable.

3. 3

   Access pumps

   Unbolt and tilt the cab forward to access the hydrostatic drive pumps.

4. 4

   Locate pump

   Locate the right-hand drive pump (typically a Bosch Rexroth A20VG or A22VG tandem pump).

5. 5

   Disconnect harness

   Disconnect the electrical harness from the right swash plate angle sensor.

6. 6

   Remove mounting screws

   Remove the two mounting screws securing the sensor to the pump housing.

7. 7

   Remove sensor

   Carefully pull the old sensor straight out.

8. 8

   Install new sensor

   Insert the new sensor, ensuring that the mechanical tang/linkage properly engages the swash plate mechanism inside the pump.

9. 9

   Reinstall screws

   Reinstall the mounting screws (Note: OEM sensors usually do not ship with new screws; reuse the old ones or procure locally).

10. 10

    Reconnect and reassemble

    Reconnect the electrical harness, lower the cab, and reconnect the battery.

11. 11

    Clear codes

    Use an electronic service tool (EST) or the machine's diagnostic monitor to clear the UCM fault codes.

12. 12

    Test drive

    Perform a test drive to verify that the machine tracks straight, responds correctly to joystick inputs, and the code does not return.