New Holland UCM 5603 – UCM: Aux Control Function: Solenoids Return Open Circuit

This fault code indicates that the control module has detected a break in the electrical continuity (an open circuit) on the return (ground) side of the auxiliary hydraulic control solenoids. Because the circuit is open, electrical current cannot flow through the solenoid coils, meaning the machine will be unable to actuate the auxiliary hydraulic functions (used for running attachments).

• L213
• L215
• L216
• L218
• L220
• L221
• L223
• L225
• L228
• L230
• L234
• C227
• C232
• C234
• C237
• C238
• C245

1. 1

   Inspect the wiring harness leading to the loader control valve block for severed wires, chafing against the chassis, or unplugged connectors at the auxiliary solenoids.

2. 2

   Disconnect the auxiliary solenoid connectors and measure the resistance across the solenoid coil pins with a multimeter (a healthy coil reads 10 to 12 ohms; 'OL' indicates a broken/open coil).

3. 3

   If the coil tests good, check the continuity of the return wire from the solenoid connector back to the UCM harness connector.

4. 4

   Check the UCM connectors and the solenoid connectors for water intrusion, corrosion, or pins that have been pushed back out of the plastic housing.

1. 1

   Prepare the Machine

   Lower the boom completely (or engage the boom locks if it must be raised for access). Turn off the ignition and engage the battery disconnect switch (or disconnect the negative battery cable).

2. 2

   Access the Valve Block

   Tilt the cab forward (following the operator's manual safety procedures) to access the main loader control valve block where the auxiliary solenoids are mounted.

3. 3

   Repair the Wiring (If Applicable)

   If the diagnostic tests revealed a broken return wire, locate the break. Cut out the damaged section and splice in a new wire using marine-grade, heat-shrink butt connectors to prevent future moisture intrusion.

4. 4

   Replace the Solenoid Coil (If Applicable)

   Disconnect the electrical pigtail from the faulty auxiliary solenoid. Remove the retaining nut at the end of the solenoid cartridge stem. Slide the faulty coil off the valve stem. (Note: You usually do not need to open the hydraulic system or remove the valve cartridge just to replace the coil). Slide the new OEM coil onto the stem, reinstall the retaining nut, and plug in the connector.

5. 5

   Reassembly and Testing

   Lower and secure the cab. Reconnect the battery. Turn the ignition on, clear the UCM fault codes using the diagnostic menu or a scan tool, and test the auxiliary hydraulics with an attachment to verify the repair.