Case IH 1916 – VCM / UCM: VCM / UCM - Rail 12VU1 - Right And Left Pumps Forward Input Power Off

The controller has detected a loss of voltage (Power Off) on the specific internal power rail designated as 12VU1. This specific power rail supplies voltage to the forward input solenoids for the right and left hydrostatic drive pumps. When this rail loses power, the machine will typically lose forward drive capability and log a red master warning lamp.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR130
• SR160
• SR175
• SR200
• SR250
• SV185
• SV250
• SV300
• TR320
• TV380

1. 1

   Check the main fuse box for blown fuses related to the UCM/VCM power supply or EH controls

2. 2

   Test the UCM Power Relay (12V 35A micro relay) to ensure it is properly switching power to the module

3. 3

   Inspect the wiring harness running from the UCM to the hydrostatic pump solenoids for chafing, pinched wires, or melted insulation that could be shorting to the chassis ground

4. 4

   Disconnect the electrical connectors at the right and left forward drive pump solenoids and measure resistance across the coil pins to check for a dead short

5. 5

   Verify that the UCM itself is receiving proper main battery voltage and ground

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes during repair.

2. 2

   Replace Blown Fuses/Relays

   If a fuse protecting the UCM or the 12VU1 circuit is blown, replace it. If the UCM power relay is faulty, swap it with a known good relay of the same amperage.

3. 3

   Repair Harness Shorts

   If the diagnostic checks revealed a short to ground in the chassis or cab EH wiring harness, splice and repair the damaged wires using weather-sealed heat-shrink connectors, or replace the harness section entirely if heavily damaged.

4. 4

   Replace Faulty Solenoids

   If a forward pump solenoid failed the resistance test (shorted out), unthread the faulty solenoid from the hydrostatic pump control valve and install a new one.

5. 5

   Replace the UCM (If Necessary)

   If the wiring and solenoids are perfectly intact but the 12VU1 rail remains dead, the UCM must be replaced. Unplug the multi-pin connectors from the UCM, unbolt the module from its mounting bracket, and install the new unit.

6. 6

   Reprogramming

   Note that a new UCM will be blank and must be flashed/programmed by a Case IH dealer using the EST (Electronic Service Tool) to match your specific machine's configuration.

7. 7

   Test Operation

   Reconnect the battery, clear the inactive fault codes, and test the machine's forward drive functions to ensure the code does not return.