Case IH 1979-03 - UCM – UCM: Rear pilot head #6 reporting supply voltage high

Fault code 1979-03 indicates "Rear pilot head #6 reporting supply voltage high." The "pilot head" is the electro-hydraulic remote (EHR) actuator mounted on top of the remote valve body. It controls the hydraulic spool movement based on CAN bus commands. An FMI 03 (Voltage High) or internal controller fault means the pilot head's internal circuitry is detecting an over-voltage condition or has suffered an internal failure. When a pilot head fails in this manner, it often corrupts or "kills" the CAN bus communication, causing other remote valves on the same circuit to go offline or become unresponsive.

• MAGNUM AFS Connect
• Magnum 180
• Magnum 200
• Magnum 210
• Magnum 225
• Magnum 235
• Magnum 240
• Magnum 250
• Magnum 280
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• Puma 140
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• Puma 180-260 CVX

1. 1

   Isolate the CAN Bus: Unplug the electrical connector specifically at the #6 rear remote pilot head. If the rest of the remote valves suddenly come back online and function normally, the #6 pilot head has an internal short that is pulling down the CAN bus network.

2. 2

   Wiring & Resistance Check: With the remote valve connector unplugged, use a multimeter to check the resistance of the CAN wiring between terminals 2 and 3 (typically blue and red wires). The resistance should be approximately 120 Ω. If it is not, trace the wiring harness for a short to power or a broken wire.

3. 3

   Check for Spool Binding: Though a voltage code usually points to an electrical failure inside the pilot head, ensure the mechanical spool inside the valve body isn't heavily worn or binding, which can overwork the actuator.

1. 1

   Preparation

   Relieve all hydraulic pressure from the system and thoroughly clean the area around the #6 rear remote valve to prevent dirt from entering the hydraulic system.

2. 2

   Removal

   Disconnect the electrical harness connector from the faulty pilot head. Remove the hex socket screws (typically M5 x 20mm) securing the pilot head to the valve slice/body.

3. 3

   Extraction

   Carefully lift the faulty pilot head assembly off the valve body.

4. 4

   O-Rings

   Inspect and replace the small O-rings located between the valve slice and the pilot head.

5. 5

   Installation

   Lubricate the new O-rings with clean hydraulic oil, seat the new pilot head assembly, and torque the hex socket screws to spec. Reconnect the electrical harness.

6. 6

   Reassign Valve Addresses (Crucial)

   The UCM will not automatically recognize the new pilot head. You must use the tractor's diagnostic menu (e.g., the "HK" menu on the armrest display, Channel 1) or the Case IH Electronic Service Tool (EST) to renumber/reassign the valves. This tells the controller which cab lever operates the newly installed valve.

7. 7

   Calibration

   Perform the EHR valve calibration procedure using the EST or armrest display to tune the valve for proper spool movement and flow.