Case IH 6005 – TCU (Transmission Control Unit) or Armrest Controller (ARM): MFD/Diff Lock - Rear Differential Lock and Auto Differential Lock (Only CCH): 1. Diff Lock On and Auto Diff Lock switches are both active.

The system has detected an invalid state where both the manual "Diff Lock On" switch and the "Auto Diff Lock" switch are sending an "active" (ON) signal at the exact same time. Because these functions conflict, the system disables the differential lock to prevent mechanical damage and logs the fault.

• Magnum
• Case IH Magnum Series
• Case IH Steiger Series

1. 1

   Check the physical state of both the manual Diff Lock and Auto Diff Lock switches on the armrest. Cycle them firmly a few times to see if a switch is physically stuck, jammed by debris, or has a collapsed internal spring.

2. 2

   Access the tractor's in-cab display/diagnostic menu to monitor the live input states of the armrest switches. This will tell you exactly which switch (Manual or Auto) is stuck "closed" (active) electronically.

3. 3

   Inspect the wiring harness and connectors underneath the armrest control panel. Look for damaged wiring, loose connectors, bent pins, or a short circuit (short to 12V or ground) that could be sending a false "active" signal to the controller.

4. 4

   Verify there are no accompanying communication codes (such as 6004 or 6006), which would indicate a broader CAN-BUS communication failure between the Armrest controller and the TCU rather than a simple switch failure.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery ground cable to prevent electrical shorts while working inside the armrest.

2. 2

   Access the Armrest Internals

   Carefully remove the retaining screws or plastic clips holding the CCH armrest control panel/bezel in place. Lift the panel to expose the switch wiring.

3. 3

   Test the Switches

   Using a multimeter, test the continuity of both the manual Diff Lock and Auto Diff Lock switches. If either switch shows continuity (closed circuit) while in the "OFF" position, the switch has failed internally.

4. 4

   Remove the Faulty Switch

   Disconnect the electrical pigtail/connector from the faulty switch. Unclip or unscrew the switch from the armrest panel.

5. 5

   Install the Replacement

   Snap or screw the new OEM switch into the armrest panel and securely reconnect the electrical harness.

6. 6

   Reassembly

   Carefully tuck the wiring back into the armrest cavity and reinstall the control panel cover. Reconnect the battery.

7. 7

   Clear Codes and Calibrate

   Turn the ignition on, navigate to the diagnostic menu, and clear the 6005 fault code. Test both the manual and auto differential lock functions to ensure normal operation and verify the code does not return.