Case IH 518049-02 - ACM – ACM: Auto differential lock switch circuit fault

The controller is receiving an unexpected, fluctuating, or out-of-range voltage signal from the differential lock switch circuit. This is typically caused by a physically stuck switch, a short circuit, or a loose electrical connection.

• MAGNUM AFS Connect
• Maxxum
• Puma
• Magnum
• Optum
• MXM series

1. 1

   Inspect the auto differential lock switch on the armrest console for physical damage, sticking, or dirt/debris that might be preventing the switch from returning to its neutral position.

2. 2

   Access the underside of the armrest and inspect the wiring harness connecting to the switch. Look for loose connector pins, corrosion, or wires that may have chafed against the console housing.

3. 3

   Using a multimeter, test the switch for proper continuity when pressed and released. Verify that the reference voltage coming from the ACM is steady and not fluctuating.

4. 4

   Use the tractor's AFS Pro display diagnostic menu to check for other related CAN bus communication errors or switch faults that might indicate a broader electrical issue.

1. 1

   Safety First

   Park the tractor on a level surface, lower all implements to the ground, turn off the engine, and remove the key. Disconnect the battery ground strap to prevent electrical shorts.

2. 2

   Access the Switch

   Carefully pry up or remove the necessary trim panels on the armrest console to access the underside of the switch panel.

3. 3

   Disconnect

   Locate the auto differential lock switch and disconnect its electrical wiring harness connector.

4. 4

   Remove

   Squeeze the retaining tabs on the sides of the switch body and push it up through the console panel to remove it.

5. 5

   Install New Switch

   Snap the new replacement switch into the armrest panel, ensuring it is seated flush.

6. 6

   Reconnect

   Plug the electrical connector back into the switch, ensuring the locking tab clicks securely into place.

7. 7

   Reassemble

   Reinstall the armrest trim panels.

8. 8

   Test

   Reconnect the battery ground strap, turn the key on, and clear the fault codes using the diagnostic display. Start the tractor and engage/disengage the auto differential lock to confirm the fault does not return and the system operates correctly.