Case IH 4255 - UCM – UCM (Universal Control Module / Universal Controller): Hydraulic Master Switch Circuit Anomaly

The Universal Control Module (UCM) has detected an electrical anomaly in the circuit for the Hydraulic Master Switch, indicating either an open circuit or a short to ground.

• MAXXUM T4E
• VESTRUM CVX
• Case IH Puma Series (Puma 130, 145, 150, 160, 165, 175, 200, 215, 225 CVX/CVT)
• Case IH Maxxum Series (Maxxum 110, 120, 130, 140 CVX / Multicontroller)
• Case IH Farmall Series (95U, 105U, 115U Pro EP)

1. 1

   Check Fuses: Verify the power supply to the Universal Controller and hydraulic systems. Check the 5A Mini fuse (F-051) for the Universal Controller. On some models like the Farmall U Pro, check fuse F-007 (Hydraulic master switch).

2. 2

   Inspect the Switch: Locate the Hydraulic Master Switch, which is typically located on the armrest control unit or the worklamps control panel.

3. 3

   Wiring Harness Inspection: Check the wiring harness running from the switch to the UCM (the UCM is often located behind the operator's seat). Look for chafed wires causing a short to ground or disconnected plugs causing an open circuit.

1. 1

   Disconnect Power

   Always disconnect the negative battery cable before performing electrical repairs to prevent damage to the UCM.

2. 2

   Access the Switch

   Remove the trim panels to access the armrest control unit or side console where the Hydraulic Master Switch is mounted.

3. 3

   Inspect Connections

   Unplug the connector to the Hydraulic Master Switch. Inspect the pins for corrosion, moisture, or pushed-out terminals.

4. 4

   Test the Switch

   Use a multimeter to test the switch for internal continuity. If the switch fails to close the circuit when toggled, it has failed internally and must be replaced.

5. 5

   Test the Harness

   If the switch is functional, use a multimeter to test the wiring harness between the switch connector and the UCM (Auxiliary Control Unit). Test for continuity from end-to-end (to rule out an open circuit) and test for continuity to ground (to rule out a short to GND).

6. 6

   Repair

   Repair any broken or chafed wires in the harness, or replace the switch if it failed the continuity test.

7. 7

   Reassemble and Test

   Reconnect the switch and the UCM. Reconnect the battery, turn the key on, and verify if the fault code clears and the hydraulic master switch functions properly.