New Holland UCM 5231 – UCM (Universal Control Module): Boom Raise/Lower: Solenoid Lower (B) Supply Open Circuit

The control module has detected a break (open circuit) in the electrical supply circuit to the "Lower B" solenoid on the loader arm directional control valve. This means power cannot reach the solenoid to actuate the boom lower function, usually due to a disconnected plug, a severed wire, or a burned-out (open) solenoid coil.

• L213
• L215
• L218
• L220
• L223
• L225
• L228
• L230
• L234
• C227
• C232
• C238
• B90B
• B95D
• B100B
• B110D
• B115B

1. 1

   Inspect the wiring harness routing from the UCM to the main loader arm control valve for pinched wires, rodent damage, or chafing against the chassis.

2. 2

   Disconnect the plug at the 'Lower B' solenoid on the loader arm valve and check for pushed-back pins, water intrusion, or corrosion.

3. 3

   Measure the resistance across the pins of the Lower B solenoid coil using a multimeter (an 'OL' reading indicates an internal failure).

4. 4

   Check for continuity on the supply wire from the UCM harness connector to the solenoid connector, and verify the ground/return circuit is intact.

5. 5

   Verify the UCM power supply fuses (e.g., UCM Unswitched F-026, UCM Battery Fuse) are intact.

1. 1

   Secure the Machine

   Park the machine on a level surface. If the loader arms are raised, you must secure them using the mechanical hydraulic cylinder lock / loader valve lock before working under them. Otherwise, safely lower the boom to the ground.

2. 2

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent accidental short circuits.

3. 3

   Access the Valve

   Locate the main loader arm directional control valve (usually under the cab/floorboards depending on the model).

4. 4

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a broken wire or damaged connector, splice in a new section of wire or install a replacement pigtail connector. (Note: Broken connectors at the valve are a common failure point).

5. 5

   Replace the Solenoid (If Applicable)

   If the solenoid coil tested open, remove the retaining nut holding the coil to the valve cartridge. Slide the old coil off and slide the new OEM coil on. Torque the retaining nut to OEM spec.

6. 6

   Reassembly

   Reconnect the electrical plug to the solenoid. Reconnect the battery.

7. 7

   Clear Codes and Test

   Use the New Holland Electronic Service Tool (EST) or the in-cab diagnostic menu to clear the UCM 5231 fault code. Start the machine and test the boom raise/lower functions to ensure the open circuit is resolved.