Case IH 518848-04 - VCM – UCM / VCM: Rail 12VF2 - Bucket Extend Input Power Off / 12VF2 supply voltage low

The control module has detected that the 12-volt supply voltage on its internal power rail '12VF2' is below the operational limit or shorted to ground. This specific power rail supplies voltage to the Bucket Extend / Proportional Auxiliary Extend solenoid.

• MAGNUM AFS Connect
• SR130
• SR150
• SR175
• SR200
• SR220
• SR250
• SV185
• SV250
• SV300
• TR270
• TR320
• TV380

1. 1

   Verify that the battery is fully charged and the alternator is outputting correct voltage to rule out system-wide low voltage.

2. 2

   Disconnect the electrical connector at the Bucket Extend / Aux Extend solenoid and check if the fault code changes to an 'Open Circuit' code (indicating an internally shorted coil).

3. 3

   Trace the wiring harness from the UCM/VCM to the loader control valve (bucket extend solenoid) and look for pinched wires, chafing against the chassis, or melted insulation.

4. 4

   Inspect the main connectors at the UCM/VCM for water intrusion, corrosion, or bent pins causing voltage drops or shorts.

1. 1

   Disconnect Power

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

2. 2

   Inspect and Repair Wiring

   If the harness inspection revealed chafed or bare wires shorting to the frame (especially near the loader arm pivot points or valve block), repair the damaged section using weather-sealed heat shrink connectors.

3. 3

   Test/Replace the Solenoid

   Using a multimeter, measure the resistance (Ohms) across the pins of the Bucket Extend solenoid. If the reading is near zero (dead short) or out of OEM spec, remove the retaining nut, slide the old solenoid coil off the valve cartridge, and install a new one.

4. 4

   Test the UCM Power Supply

   Reconnect the battery. Back-probe the UCM power and ground pins to ensure the module is receiving full battery voltage.

5. 5

   Replace the UCM (If Necessary)

   If the wiring is perfectly intact and the solenoid is not shorted, the UCM has likely suffered an internal failure on the 12VF2 power rail. Disconnect the harnesses, unbolt the UCM bracket, and install a replacement module. (Note: A new UCM will require a dealer service tool (EST) to flash the software and calibrate the EH controls to your specific machine).

6. 6

   Clear Codes and Test

   Clear the inactive fault codes and operate the bucket extend/retract functions to verify the repair.