Case IH 518917-02 - UCM – UCM: Plausibility check failure (divergence/mismatch) in the front hitch exterior inching switch

The control module is receiving an invalid, conflicting, or illogical signal from the exterior switch used to incrementally raise or lower the front hitch from outside the cab. This usually occurs if the switch is stuck, internally shorted (sending both "up" and "down" signals simultaneously), or if there is a wiring issue distorting the expected signal values.

• MAGNUM AFS Connect
• Magnum 310 AFS Connect
• Magnum 340 AFS Connect
• Magnum 380 AFS Connect
• Magnum 400 AFS Connect
• Magnum Rowtrac AFS Connect

1. 1

   Check for related code 518917-04 - UCM, which indicates low voltage on the same circuit and points heavily toward a wiring short to ground or a disconnected harness

2. 2

   Inspect the exterior inching switch located near the front hitch for physical damage, sticking buttons, or heavy debris/moisture intrusion that could cause the switch contacts to bridge

3. 3

   Inspect the front hitch wiring harness and its connection to the chassis harness for pinched wires, rubbed insulation, or corroded connector pins

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes during testing.

2. 2

   Access the Switch

   Locate the exterior inching switch assembly mounted on the front hitch frame.

3. 3

   Disconnect and Inspect

   Unplug the switch connector. Inspect both the switch side and the harness side for green corrosion, water ingress, or pushed-out pins. Clean with electrical contact cleaner if necessary.

4. 4

   Test the Switch

   Using a multimeter, test the continuity of the switch. It should only show continuity on the respective circuits when the "Up" or "Down" buttons are actively pressed. If it shows continuity without being pressed, or fails to show continuity when pressed, the switch has failed internally.

5. 5

   Repair/Replace

   If the switch fails the continuity test, replace the switch assembly. If the switch is good, trace the front hitch harness back to the UCM, repairing any damaged wires.

6. 6

   Reassemble and Clear Codes

   Reconnect the switch, reconnect the battery, and turn the key on. Clear the UCM fault codes and test the front hitch exterior inching function to verify the repair.