Case IH 1943-03 - UCM – UCM: Aux Valve 3 Port Flow Command - Voltage above normal, or shorted to high source

The controller is detecting higher-than-expected voltage on the circuit commanding the #3 rear auxiliary hydraulic valve, usually indicating a short to battery voltage.

• MAGNUM AFS Connect
• Magnum Series (e.g., AFS Connect 180-380)
• Puma Series (e.g., 140-175)
• Axial-Flow Combines
• Early Riser 2000 Series Planters

1. 1

   Visually inspect the wiring harness leading to the Rear Aux Valve #3 pilot head for chafing, melted insulation, or pinched wires that could expose the signal wire to a 12V power source.

2. 2

   Inspect the solenoid connection at the pilot head (AMP Junior Timer or Deutsch DT04 connectors) for water intrusion, corrosion, or bent pins bridging the voltage.

3. 3

   Disconnect the Aux Valve 3 pilot head and use a multimeter to check the signal wire for voltage with the key on. If 12V is present when it shouldn't be, the short is in the harness or the UCM.

1. 1

   Isolate the Circuit

   Turn off the machine and disconnect the electrical connector at the Rear Pilot Head #3 (Aux Valve 3).

2. 2

   Test the Harness

   Turn the key to the ON position. Probe the command signal wire at the valve connector. If it reads battery voltage (approx. 12V) without the valve being commanded, there is a short to power in the harness.

3. 3

   Trace to the UCM

   Disconnect the corresponding multi-pin OEM connector at the UCM. Check the harness wire for continuity to power. If the short disappears when the UCM is unplugged, the UCM itself may have an internal short. If the short remains, the wiring harness is damaged.

4. 4

   Repair/Replace

   Repair the damaged section of the wiring harness. If the harness and UCM test fine, the internal solenoid coil of the pilot head itself may be shorted to its own power supply, requiring a replacement of the pilot head.

5. 5

   Clear and Verify

   Reconnect all components, clear the 1943-03 code from the UCM, and actuate Aux Valve 3 to ensure the code does not return and hydraulic flow is commanded properly.