Case IH 4431 – UCM (Universal Control Module) or Hyd (Hydraulic Controller): Park Brake Pressure Switch (Plausibility Check With Solenoid Valve)

This code indicates a plausibility mismatch between the commanded state of the park brake solenoid valve and the actual hydraulic pressure reading from the park brake pressure switch. When the controller commands the park brake solenoid to release the brake, it expects the pressure switch to confirm that pressure is present.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Case TR310B
• Case SR175

1. 1

   Visual & Fluid Inspection: Check the hydraulic fluid level. Inspect the machine for blown hydraulic hoses or severe leaks. A sudden loss of hydraulic pressure (such as a blown hose in the field) will trigger this code because the pressure switch will fail to detect the required pressure to release the brake.

2. 2

   Wiring & Connector Check: Inspect the 2-pin electrical connectors and wiring harnesses going to both the Park Brake Pressure Switch and the Park Brake Solenoid. Look for frayed wires, corrosion, open circuits, or shorts to ground/power.

3. 3

   Component Testing: Test the Park Brake Solenoid to ensure it is receiving voltage and actuating when the park brake button is toggled. Test the Park Brake Pressure Switch with a multimeter to verify it opens and closes correctly when hydraulic pressure is applied or removed.

4. 4

   Hydraulic Pressure Test: Check the actual hydraulic system pressure at the park brake release circuit to determine if the issue is hydraulic (no pressure reaching the switch) or electrical (pressure is present, but the switch/solenoid is failing).

1. 1

   Secure the Machine

   Lower the boom/loader arms to the ground, turn off the engine, and relieve all hydraulic system pressure before servicing.

2. 2

   Address Hydraulic Leaks

   If a blown hose or leak was found during diagnosis, replace the damaged hose and refill the hydraulic fluid to the proper level.

3. 3

   Replace the Park Brake Pressure Switch

   Disconnect the 2-pin electrical connector from the pressure switch. Unscrew the faulty switch from the hydraulic valve block. Install the new pressure switch (ensure any required O-rings or thread sealants are used per OEM spec). Reconnect the electrical harness.

4. 4

   Replace the Park Brake Solenoid

   Disconnect the electrical connector from the solenoid coil. Remove the retaining nut holding the coil to the valve stem, and slide the coil off. If the cartridge valve itself is stuck, unscrew the cartridge from the manifold. Install the new solenoid coil (and cartridge valve if replaced), tighten the retaining nut, and reconnect the harness.

5. 5

   Clear Codes and Test

   Turn the battery power back on, clear the fault codes using a diagnostic tool (or by cycling the key), and start the machine. Toggle the park brake switch to ensure the brake engages and disengages properly without throwing the code.