Case IH 4781 – UCM (Universal Control Module): Solenoid Valve Supply Open Circuit

The control module has detected an open circuit in the supply line to a solenoid valve. This indicates a broken electrical path, typically caused by a severed wire, a disconnected or corroded harness plug, a blown fuse, or a failed (open) solenoid coil.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR130
• SR175
• SR200
• SV185
• SV250
• TR270
• TR320
• TV380

1. 1

   Identify the affected solenoid (most commonly the Two-Speed Solenoid or Loader Control Valve/EH control solenoids).

2. 2

   Inspect the wiring harness for rub-throughs, especially where it feeds into the canopy/cab, behind the foot kick panel under the seat, and where it crosses under the hydraulic pumps.

3. 3

   Test the solenoid coil by disconnecting the plug and measuring resistance (Ohms) across the coil pins; an infinite (OL) reading indicates an open/broken internal coil.

4. 4

   Check connections and grounds for pushed-out pins, moisture, or corrosion, and locate and clean the main ground posts located under the cab.

5. 5

   Check UCM output by back-probing the connector with the key on to verify the correct reference voltage is being sent to the solenoid.

1. 1

   Park and Secure

   Park the machine on a level surface, lower the loader arms (or engage the cylinder lock if they must be raised), turn off the engine, and disconnect the negative battery cable.

2. 2

   Expose the Routing

   Tilt the cab forward and lock it into place to gain access to the UCM, the main wiring harness, and the hydraulic control valves.

3. 3

   Repair Wiring

   If a broken wire was found during diagnostics (especially near cab pivot points or under the seat), strip back the damaged section, solder in a new section of wire, seal it with marine-grade heat shrink, and wrap the repaired area in protective wire loom.

4. 4

   Replace the Solenoid

   If the coil tested open, clean the area around the hydraulic valve block. Unplug the electrical connector, remove the retaining nut to slide the coil off or unscrew the entire cartridge, install the new solenoid/coil (lubricate O-rings with clean hydraulic fluid if replacing the cartridge), torque to OEM specifications, and reconnect the plug.

5. 5

   Reassemble and Test

   Lower and secure the cab, reconnect the battery, and turn the key on. Clear the fault codes in the instrument cluster and operate the machine (specifically two-speed or loader functions) to ensure the code does not return.