Case IH 518857-04 - VCM – VCM: VCM - Rail 12VT1 - Two Speed Input Power Off

The control module has detected that the voltage on the internal or external power supply rail designated as '12VT1' has dropped below the normal operational limit.

• MAGNUM AFS Connect
• SR130
• SR150
• SR175
• SV185
• SR200
• SR220
• SR250
• SV250
• SV300
• TR270
• TR320
• TV380
• Magnum AFS Connect series
• Steiger series
• Puma series
• T7 series
• Early Riser Planters
• Patriot Sprayers

1. 1

   Check the cab/chassis fuse panel for blown fuses related to the VCM/UCM and transmission/two-speed controls

2. 2

   Verify that the tractor/machine battery voltage is between 12V and 14V and that the alternator is charging properly

3. 3

   Trace the wiring from the VCM to the Two-Speed solenoid (or specific component powered by the 12VT1 rail) and look for chafed wires, pinched harnesses, or exposed copper shorting to ground

4. 4

   Disconnect the Two-Speed solenoid (or corresponding actuator) and check its resistance to rule out an internal short

5. 5

   Ensure the main power and ground connections to the VCM/UCM are clean, tight, and free of corrosion

1. 1

   Disconnect Power

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

2. 2

   Replace Blown Fuses

   If the diagnostic checks revealed a blown fuse for the 12VT1 circuit, replace it with a fuse of the exact same amperage rating.

3. 3

   Isolate the Short

   If the new fuse blows immediately upon key-on or when the two-speed function is engaged, disconnect the two-speed solenoid. Insert a new fuse. If the fuse does not blow, the solenoid is internally shorted and must be replaced. If the fuse still blows, the short is in the wiring harness between the VCM and the solenoid.

4. 4

   Repair Wiring

   Repair any damaged sections of the wiring harness using OEM-approved weather-sealed connectors and heat shrink.

5. 5

   Replace the VCM/UCM

   If the fuses are good, the wiring tests perfectly for continuity, and the solenoid is functional, the VCM itself may have a burnt internal power trace on the 12VT1 rail. The module will need to be replaced and reprogrammed by a dealer.

6. 6

   Clear Codes

   Reconnect the battery, turn the key on, and use the EST (Electronic Service Tool) or the in-cab display to clear the inactive fault codes. Test the machine's two-speed or transmission functions to verify the repair.