Case IH 2913 – Transmission Control Module (Trans / TCU) / Universal Control Module (UCM): 12VH voltage supply is low. (possible blown fuse*)

The control module is detecting that the voltage on the specific '12VH' power supply rail has dropped below the acceptable operating threshold (often below 8 volts).

• Magnum
• Case IH Magnum Series (235, 260, 290, 315, 340 Series 4)
• Case IH Steiger Series (350 through 600)
• Case IH MX / TG Series

1. 1

   Verify that the tractor's main batteries are fully charged and the alternator is outputting proper system voltage.

2. 2

   Locate the main cab fuse panel or the specific UCM enclosure and inspect the fuse designated for the 12VH circuit (sometimes labeled as Fuse 12 or PWR Fuse 1).

3. 3

   Visually inspect the wiring harness running from the fuse block to the Transmission Controller for pinch points, chafed insulation rubbing against the frame, or heat damage.

4. 4

   Disconnect the harness at the Transmission Controller and check connector integrity for moisture, corrosion, or pushed-out pins.

1. 1

   Power Down

   Turn the key switch to the OFF position, engage the parking brake, and disconnect the negative battery cable to prevent accidental shorts during testing.

2. 2

   Check/Replace the Fuse

   Access the fuse panel and pull the 12VH supply fuse. Test it with a multimeter for continuity. If it is blown, replace it with a new fuse of the exact same amperage rating.

3. 3

   Short-to-Ground Test

   Reconnect the battery and turn the key to the ON position. If the new fuse blows immediately, there is a dead short to ground in the 12VH circuit.

4. 4

   Trace and Repair Wiring

   If a short is present, use a multimeter to trace the 12VH wire from the fuse block to the transmission controller. Locate the damaged section of the wire (often where the harness bends or contacts metal). Cut out the damaged section, splice in new wire using weather-sealed crimp connectors, and protect it with heat shrink and split loom.

5. 5

   Clear Codes and Test

   Once the wiring is repaired and a good fuse is installed, power up the machine. Use the AFS Pro monitor or the Electronic Service Tool (EST) to clear the inactive fault codes.

6. 6

   Operational Check

   Shift the tractor through Forward, Neutral, and Reverse to ensure the transmission engages properly and the code does not return.