New Holland UCM 1900 – UCM (Universal Control Module): Power Supply: UCM Ground Fault

This fault code indicates that there is a short to ground in the power supply circuit feeding the Universal Control Module (UCM). The system has detected that the voltage on the power supply line has dropped abnormally, typically due to a compromised wire touching the machine's chassis or an internal short within the module itself.

• L213
• L216
• L218
• L220
• L221
• L223
• L225
• L228
• L230
• L234
• C227
• C232
• C234
• C237
• C238
• C245
• T7 series
• CR series

1. 1

   Ensure the battery disconnect switch is functioning properly and the negative cable is secure.

2. 2

   Check the main fuse box (WIC Fuse Box) for blown fuses. Pay special attention to the 3A Micro, 5A Mini, and 10A Mini fuses that protect the UCM and chassis circuits.

3. 3

   Inspect the chassis wire harness routing to the UCM for visible chafing, pinching, or melted insulation that could cause a short to the frame.

4. 4

   Disconnect the UCM connector. Using a multimeter, probe the ECU harness side of the connector on the power supply pins to check for continuity to ground.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent further electrical damage.

2. 2

   Access the UCM

   Locate the Universal Control Module and carefully disconnect the main wiring harness.

3. 3

   Isolate the Short

   If your multimeter test showed continuity to ground on the power wire, trace the wire back through the chassis harness. Look for areas where the harness rubs against metal brackets or moving parts.

4. 4

   Repair or Replace Wiring

   If a damaged wire is found, repair the wire using proper weather-sealed connectors, or replace the entire chassis wire harness if the damage is extensive.

5. 5

   Test the UCM

   If the wiring harness tests perfectly fine (no short to ground in the harness), the ground fault is likely internal to the UCM itself. In this case, the UCM must be replaced.

6. 6

   Reassemble and Clear Codes

   Reconnect the UCM and the battery. Replace any blown fuses. Turn the key on and use a diagnostic tool to clear the UCM 1900 fault code. Verify the repair by operating the machine to ensure the code does not return.