Case IH 518855-04 - VCM – VCM: 12VS1 supply voltage low

The Failure Mode Identifier (FMI) "04" indicates that the voltage is below normal or shorted to a low source. The control module is detecting that the voltage on the specific "12VS1" power rail has dropped below the acceptable operational limit.

• MAGNUM AFS Connect
• Steiger AFS Connect
• Axial-Flow series
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Planters

1. 1

   Verify that the tractor's main battery and alternator voltage are within normal operating ranges (approx. 12.5V - 14.4V).

2. 2

   Check the 12VS1 fuse in the cab fuse and relay panel (Steiger: F-017 10A, Magnum: F-023 20A, Axial-Flow: F-027 15A).

3. 3

   Inspect the wiring harness leading to actuators powered by the 12VS1 rail for chafing, melting, or a short to ground.

4. 4

   Use a multimeter to measure voltage at the fuse terminal and at the corresponding 12VS1 input pin on the VCM to check for an open circuit.

1. 1

   Disconnect Power

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

2. 2

   Access the Fuse Panel

   Remove the rubber liner and tray in the rear cab wall to access the fuse block.

3. 3

   Replace or Repair

   If the 12VS1 fuse is blown, replace it with a fuse of the exact same amperage. If a short to ground was found in the harness during diagnostics, repair the damaged wire using OEM-approved heat-shrink butt connectors and re-loom the harness. If a downstream solenoid powered by the 12VS1 rail is internally shorted, replace the solenoid.

4. 4

   Check VCM Connections

   Disconnect the main harness from the VCM. Inspect the pins for corrosion, bent terminals, or moisture intrusion. Clean with contact cleaner and apply dielectric grease before reconnecting.

5. 5

   Test and Clear

   Reconnect the battery. Turn the key to the ON position and use the Pro 1200 display (or EST diagnostic tool) to clear the inactive 518855-04 fault code. Operate the machine's hydraulic functions to ensure the code does not return.