Case IH 6004 – TCU (Transmission Control Unit) and Armrest Controller: MFD/Diff Lock

CAN-BUS indicating Rear Diff Lock Switch failed in the armrest. The system has detected an open circuit, short to ground, or a communication failure regarding the differential lock switch inputs.

• Magnum
• Steiger T4B
• Case IH Magnum 235 - 340 (Series 4)
• Case IH MX Magnum Series (MX210, MX230, MX255, MX285)
• Case IH Steiger Series (e.g., 280-535, 435)
• Case IH MXM Series (MXM120 - MXM190)

1. 1

   Clear the error code with an approved electronic service tool and retest to rule out a transient communication glitch

2. 2

   Inspect the wiring harness and connectors between the armrest switch, the Armrest Controller, and the TCU for damaged wiring, loose connectors, or bent pins

3. 3

   Test the Rear Diff Lock Switch continuity with a multimeter (no continuity between pin 2 and 6 when OFF; continuity when momentary ON)

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the battery to prevent electrical shorts while working on the armrest console.

2. 2

   Access the Armrest Switches

   Remove the necessary trim panels on the armrest console to access the underside of the switch panel.

3. 3

   Replace Faulty Switch

   If the continuity test failed, unplug the harness connector from the Rear Diff Lock Switch (or Auto Diff Lock Switch) and pop the switch out of its mounting bezel. Snap the new switch into place and reconnect the harness.

4. 4

   Repair Wiring

   If the switch tested good but the wiring inspection revealed damage, repair the broken wires or replace the damaged harness section leading to the Armrest Controller.

5. 5

   Controller Replacement (If Necessary)

   If both the switch and wiring are fully functional, the fault lies in either the Armrest Controller or the TCU. Replace the faulty controller and recalibrate the armrest/transmission using the dealer electronic service tool.

6. 6

   Final Test

   Reconnect the battery, power up the tractor, and verify that the diff lock engages properly and the 6004 code is cleared.