Case IH 1979-02 - UCM – UCM: Loss of communication of the vehicle controller with the rear pilot head #6

The fault is triggered when the controller stops receiving CAN bus communication signals from the rear pilot head #6 (or #5), which is the electronic actuator (solenoid/pilot valve assembly) that controls the hydraulic flow for the rear remote spool valves.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect series (Magnum 280, 340, 400)
• Case IH Steiger & Quadtrac AFS Connect series (Steiger 420-620, Quadtrac 470-620)

1. 1

   Inspect the wiring harness connecting the UCM to the #6 rear pilot head for chafed wires, opens, or shorts in the CAN bus lines.

2. 2

   Disconnect the electrical plug at the #6 pilot head and check for moisture, corrosion, or bent pins.

3. 3

   Verify that the pilot head is receiving proper voltage and ground from the UCM.

4. 4

   Perform a component swap test by swapping the #6 pilot head with a known good pilot head from an adjacent remote valve (e.g., #4 or #5). If the fault code changes to match the new position, the pilot head itself has failed. If the fault remains at #6, the issue is in the wiring harness or the UCM.

1. 1

   Turn off the tractor, relieve all hydraulic system pressure, and disconnect the battery.

   Perform this step if the pilot head is determined to be faulty.

2. 2

   Locate the rear hydraulic remote valve stack at the back of the tractor and identify the #6 valve section.

3. 3

   Disconnect the electrical connector from the pilot head assembly.

4. 4

   Remove the mounting hardware (typically M5 hex socket screws) securing the pilot head to the main hydraulic valve body.

5. 5

   Remove the old pilot head assembly, ensuring no dirt or debris enters the hydraulic valve section.

6. 6

   Install the new pilot head assembly (using new O-rings/seals if required) and torque the mounting screws to specification.

7. 7

   Reconnect the electrical harness.

8. 8

   Reconnect the battery. Connect the Case IH Electronic Service Tool (EST) to the diagnostic port to clear the 1979-02 fault code and perform a calibration of the new remote valve pilot head.