New Holland UCM 5391 – UCM: Enhanced High-Flow Auxiliary Option: Solenoids Return Open Circuit

The control module has detected a break in the electrical return path (an open circuit) for the solenoids that control the Enhanced High-Flow (EHF) auxiliary hydraulic pump. This means current cannot flow through the return circuit, which is usually caused by a disconnected plug, a broken wire in the harness, or a failed (internally open) solenoid coil.

• 200 Series Skid Steer Loaders
• Compact Track Loaders
• L218
• L220
• L223
• L225
• L230
• L234
• C232
• C238

1. 1

   Verify EHF Equipment & Interlocks: Ensure the machine is actually equipped with the EHF option and that the multifunction high-pressure interlock plug (14-pin connector) is properly connected to the attachment. The EHF system requires the interlock to be satisfied to operate.

2. 2

   Visual Harness Inspection: Inspect the wiring harness leading to the EHF pump control Proportional Reducing Valve (PRV) solenoids on the hydraulic pump assembly. Look for chafed wires, rodent damage, or disconnected plugs.

3. 3

   Continuity Test (Return Circuit): Disconnect the EHF solenoid and use a multimeter to check the continuity of the return wire back to the UCM. An open circuit here confirms a wiring harness failure.

4. 4

   Solenoid Coil Resistance Test: Measure the resistance across the pins of the EHF pump control solenoid itself. If the multimeter reads 'OL' (infinite resistance), the solenoid coil has failed internally and is causing the open circuit.

5. 5

   Jumper/Adapter Check: If using an aftermarket attachment, verify that the attachment's wiring harness or jumper plug (which routes the return/interlock signals) is not damaged or missing.

1. 1

   Safety First

   Park the machine on level ground, lower the loader arms (or engage the loader locks), turn off the engine, and cycle the hydraulic controls to relieve any residual hydraulic pressure.

2. 2

   Locate the Solenoids

   Access the hydrostatic/hydraulic pump assembly (usually located under the cab, requiring the cab to be tilted). Locate the EHF pump control PRV solenoids.

3. 3

   Repair Wiring (If Applicable)

   If the diagnostic continuity test revealed a broken wire in the return circuit, repair the wire using OEM-approved weather-sealed connectors, or replace the damaged section of the harness.

4. 4

   Replace the Solenoid (If Applicable)

   If the solenoid coil tested open, disconnect its electrical connector. Unscrew the retaining nut holding the solenoid coil to the valve stem, slide the old coil off, and install the new coil. (If the entire PRV cartridge is damaged, unthread the cartridge from the pump block and install a new one, taking care to lubricate the O-rings with clean hydraulic fluid).

5. 5

   Reassembly and Clearing

   Reconnect the electrical harness. Lower and secure the cab.

6. 6

   Testing

   Turn the ignition on and use the instrument cluster or a diagnostic tool to clear the UCM 5391 fault code. Start the machine, engage the hydraulic enable switch, and test the EHF auxiliary hydraulics with an approved attachment to verify the open circuit is resolved.