Case IH 5603 – UCM (Universal Control Module): Loader Auxiliary Valve (Directional) Solenoids Return Open Circuit

This code indicates that the control module has detected a break in the electrical path (an open circuit) on the return (ground) side of the directional solenoids that control the loader's auxiliary hydraulic valve. When this circuit is open, the solenoids cannot actuate, resulting in a loss of auxiliary hydraulic functions.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Puma
• Steiger
• Maxxum

1. 1

   Visually inspect the wiring harness running from the UCM to the auxiliary hydraulic control valve block for chafed wires, pinch points, or disconnected plugs.

2. 2

   Disconnect the electrical connector at the auxiliary valve directional solenoids and check for corrosion, moisture, dirt, or pushed-back pins.

3. 3

   Measure the resistance across the pins of the directional solenoid coil using a multimeter. An 'OL' (Open Loop) reading indicates internal failure.

4. 4

   Check the continuity of the return wire from the solenoid connector back to the UCM to verify if there is a broken wire in the harness.

1. 1

   Depressurize and Power Down

   Lower the loader arms to the ground, turn off the engine, and cycle the hydraulic controls to relieve any residual hydraulic pressure. Disconnect the battery to prevent electrical shorts during repair.

2. 2

   Locate the Valve

   Locate the auxiliary hydraulic control valve block (usually located under the cab or within the loader arm chassis on skid steers).

3. 3

   Disconnect Wiring

   Unplug the wiring harness connector from the faulty directional/proportional auxiliary valve solenoid.

4. 4

   Remove the Solenoid

   Remove the retaining nut or fastener securing the solenoid coil to the valve spool stem. Slide the old solenoid off the valve cartridge. (Note: If the cartridge itself is leaking or damaged, the entire cartridge valve may need to be unthreaded and replaced).

5. 5

   Install the New Part

   Slide the new solenoid coil onto the valve stem and secure it with the retaining nut. Do not overtighten, as this can distort the coil.

6. 6

   Repair Wiring (If Applicable)

   If the diagnostic tests pointed to a harness failure rather than the solenoid, splice and repair the broken return wire using weather-sealed heat-shrink connectors, or replace the damaged connector pigtail.

7. 7

   Reassembly and Clearing Codes

   Reconnect the battery. Turn the key to the ON position. Use the Case IH Electronic Service Tool (EST) or the machine's onboard diagnostic display to clear the inactive 5603 fault code. Test the auxiliary hydraulics for proper operation.