Case IH 518593-02 - ACM – ACM: Internal fault in the front PTO engagement switch

This fault indicates a circuit error (internal fault, open circuit, or short circuit) detected in a specific switch located on the tractor's armrest console (either the A/C fan speed switch or the front PTO switch). The control module is receiving an out-of-range voltage or no signal when the switch is actuated, preventing the commanded function from operating.

• MAGNUM AFS Connect
• Magnum AFS Connect Series: 180, 200, 220, 240, 250, 280, 310, 340, 380, 400
• Puma Series: 175, 200, 215, 230
• Steiger / Quadtrac Series: 350, 400, 450, 500, 550, 600

1. 1

   Verify the exact switch triggering the fault using the Case IH Electronic Service Tool (EST) or the in-cab display.

2. 2

   Inspect the switch on the armrest for physical damage, sticking, or debris preventing full travel.

3. 3

   Lift the armrest control panel and inspect the wiring harness between the switch and the ACM. Look for chafed wires, pinched harnesses, or loose pins at the ACM connectors (specifically the 34-cavity C054M connector).

4. 4

   Disconnect the switch and use a multimeter to test for proper continuity when the switch is toggled. If the switch reads open when closed (or vice versa), the switch has failed internally.

5. 5

   Check if there is a software update available for the ACM. CNH has previously released ACM software updates (e.g., version 1.1.0.0) to resolve false switch fault codes.

1. 1

   Prepare machine

   Park the tractor on a level surface, apply the parking brake, turn off the engine, and disconnect the negative battery cable to prevent electrical shorts during repair.

2. 2

   Access armrest switches

   Carefully pry or unscrew the integrated control panel cover on the armrest to expose the internal switches and the ACM.

3. 3

   Disconnect faulty switch

   Locate the faulty switch (A/C fan speed or PTO engagement) and disconnect its electrical pigtail.

4. 4

   Replace switch

   If the switch failed the diagnostic continuity test, unclip the switch assembly from the bezel and install the replacement switch.

5. 5

   Repair wiring

   If the wiring harness is damaged, repair the broken wires or replace the affected sub-harness section connecting to the ACM.

6. 6

   Reassemble armrest

   Reconnect the switch pigtail and snap the armrest control panel back into place.

7. 7

   Restore power and clear codes

   Reconnect the battery cable and turn the ignition ON. Use the EST or the tractor's diagnostic menu to clear the inactive 518593-02 fault code.

8. 8

   Test operation

   Test the switch operation to ensure the A/C fan speed increases (or the PTO engages) and confirm the code does not return.