New Holland UCM 4431 – UCM (Universal Control Module): Park Brake Pressure Switch - Pressure Switch (plausibility check with solenoid valve)

This fault code indicates a plausibility error where the control module has sensed a disagreement between the state of the Park Brake Pressure Switch and the Park Brake Solenoid. The fault only activates when the engine is ON and the input from the pressure switch does not match the output state of the solenoid valve.

• L213
• L215
• L218
• L220
• L228
• L229
• C227
• C232
• C238

1. 1

   Use the New Holland Electronic Service Tool (EST) to verify if fault code 4431 is currently active. If not, the fault may be intermittent.

2. 2

   Check if Diagnostic Trouble Codes 4085, 4056, or 4057 are active. Resolve these first, as they indicate underlying solenoid supply issues that can trigger the 4431 plausibility error.

3. 3

   Use the EST to access the status of the park brake pressure switch and verify if the UCM is reading it as ON or OFF.

1. 1

   Inspect the Wiring Harness

   Check for any disconnections, open circuits, or shorts in the wiring harness connecting the park brake pressure switch and the park brake solenoid to the UCM.

2. 2

   Check Fuses and Relays

   Inspect the parking brake relay and relevant fuses (e.g., BT3 No 8) for blown circuits.

3. 3

   Test the Park Brake Pressure Switch

   Test the switch for internal failure. If it is malfunctioning and sending an incorrect state to the UCM, replace the switch.

4. 4

   Test the Park Brake Solenoid

   Test the solenoid valve to ensure it is actuating properly when commanded. A failed solenoid will cause a mismatch with the pressure switch reading.

5. 5

   Check Hydraulic/Mechanical Systems

   If the electrical components are functioning, check for hydraulic or mechanical failures that would prevent pressure from building or releasing. Check for low brake oil level, low brake pump pressure, or a leaking parking brake piston seal.