New Holland UCM 4072 – UCM: Ground Drive: Solenoid Left (B) Supply Short to Ground

The control module has detected that the electrical supply circuit providing power to the left hydrostatic drive pump's forward directional solenoid has shorted to a ground source (such as the machine's chassis or a ground wire). This will typically disable the left-side ground drive or cause erratic steering/movement.

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

1. 1

   Visually trace the wiring harness from the UCM to the left tandem drive pump solenoid for pinched wires, chafing, or melted insulation.

2. 2

   Disconnect the electrical connector at the left drive pump solenoid and check for continuity between the solenoid's supply pin and ground to test for an internal short.

3. 3

   With the solenoid disconnected, check the supply wire on the harness side for continuity to ground to isolate a harness short.

4. 4

   Inspect the UCM connectors for water intrusion, bent pins, or corrosion bridging the supply pin to a ground pin.

1. 1

   Disconnect Power

   Turn off the machine, engage the parking brake, and disconnect the negative battery cable to prevent electrical damage during repair.

2. 2

   Access the Drive Pumps

   Lift and secure the cab (following OEM safety procedures) to access the hydrostatic tandem drive pumps and the UCM.

3. 3

   Address Wiring Issues

   If the diagnostic tests revealed a short in the harness, locate the damaged section. Splice and repair the wire using weather-sealed heat-shrink connectors, or replace the affected chassis/EH wiring harness entirely. Secure the harness with zip ties away from moving parts or sharp edges.

4. 4

   Replace the Solenoid Coil

   If the solenoid coil tested internally shorted, remove the retaining nut holding the coil to the left forward pump control valve stem. Slide the old coil off, slide the new coil on, and torque the retaining nut to OEM specifications.

5. 5

   Reconnect and Test

   Reconnect the solenoid electrical connector and the battery negative cable. Turn the key on, clear the stored UCM fault codes using the instrument cluster or a diagnostic tool, and test the machine's ground drive functions to ensure the code does not return.

6. 6

   UCM Replacement

   If the wiring and solenoid are both in perfect condition, the UCM itself may have an internal short on that driver circuit and will need to be replaced and re-flashed by a dealer.