New Holland UCM 1915 – UCM: Power Supply: Rail 12VT1 - Two Speed Input Power OFF

The control module is not detecting the required 12-volt power on the specific internal/external power rail (12VT1) dedicated to the two-speed travel circuit. This condition typically indicates a loss of voltage due to a blown fuse, a faulty relay, an open circuit (broken wire), or a short-to-ground in the wiring harness leading to the two-speed switch or the two-speed solenoid valve.

• L213
• L215
• L216
• L218
• L220
• L221
• L223
• L225
• L228
• L230
• C227
• C232
• C234
• C237
• C238
• L175
• L180
• L185
• L190
• C185
• C190

1. 1

   Verify that the battery is fully charged and the battery quick-disconnect switch is fully in the ON position.

2. 2

   Check the main fuse/relay panel for any blown fuses or faulty relays associated with the UCM power supply and the two-speed travel circuit.

3. 3

   Test the two-speed toggle/trigger switch located on the operator control handles (joysticks) for proper continuity and operation.

4. 4

   Visually inspect the wiring harness running from the UCM to the control handle switch, and from the UCM to the two-speed solenoid valve on the hydrostatic drive pump. Look for chafed wires, pinched harnesses, or disconnected/corroded plugs.

5. 5

   Unplug the two-speed solenoid valve and use a multimeter to check the resistance of the coil. A shorted coil can pull the voltage down and cause the UCM to shut off power to the rail to protect the circuit.

1. 1

   Safely park the machine on level ground, lower the boom (or engage the boom locks), engage the parking brake, and turn off the engine.

2. 2

   Turn the battery disconnect switch to the OFF position or disconnect the negative battery cable.

   This prevents electrical shorts during repair.

3. 3

   Trace the two-speed circuit wiring to locate the short-to-ground that caused the fuse to blow.

   If a blown fuse was found during diagnostics, do not simply replace it.

4. 4

   Access the hydrostatic drive pump/motor area to locate the two-speed brake valve assembly and solenoid.

5. 5

   Disconnect the electrical connector at the two-speed solenoid.

   Clean the contacts with electrical contact cleaner if moisture or corrosion is present.

6. 6

   Repair damaged wiring harness.

   If the wiring harness is damaged (e.g., rubbed through against the chassis), cut out the damaged section, solder in new wire, and seal it with heat-shrink tubing.

7. 7

   Replace the solenoid coil or entire valve assembly.

   If the solenoid coil failed the resistance test, remove the retaining nut on the valve stem, slide the old coil off, and install a replacement coil. If the valve itself is mechanically stuck or leaking, replace the entire two-speed solenoid valve assembly.

8. 8

   Reconnect the battery, turn the ignition key to the ON position, and use the electronic display or Electronic Service Tool (EST) to clear the UCM 1915 fault code.

9. 9

   Start the machine and test the two-speed function in a safe, open area to verify the repair.