Case IH 520611-02 - ACM – ACM: PTO brake switch circuit fault

The control module has detected an electrical anomaly in the circuit that monitors or controls the Power Take-Off (PTO) brake switch. This is typically caused by an open circuit, a short to ground, a short to power (12V+), or a failure in the switch itself preventing the module from reading the correct state of the PTO brake.

• MAGNUM AFS Connect
• Puma Series (Puma 145, 150, 180, 220, 240)
• Maxxum Series (Maxxum 110, 150)
• MXU Series (MXU115, MXU135)
• Magnum Series

1. 1

   Inspect Connectors: Check the rear PTO brake switch connector (often designated as C118) and the ACM controller connector. Ensure the connectors are fully seated, not damaged, and that no pins have been pushed back into the housing.

2. 2

   Check Fuses: Verify the condition of the PTO circuit fuses. On many of these models, this is fuse F38 (Rear PTO Ignition / Rear PTO Switch & Lamp / HPL Fuse - 10A).

3. 3

   Harness Inspection: Inspect the main cab and rear wiring harnesses for rodent damage or chafing. Pay special attention to the power supply wire (often wire 2050 / Green) and the PTO brake signal wire (often wire 2120 / Tan). A short to ground on the 12V supply wire is a common cause for this fault.

4. 4

   Test the Switch: Disconnect the PTO brake switch and test it for proper continuity when manually actuated to rule out an internal mechanical failure of the switch.

1. 1

   Turn off tractor and disconnect battery

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate PTO brake switch

   Locate the PTO brake switch. Depending on the specific model, this may be located externally near the rear PTO housing or integrated into the fender/cab controls.

3. 3

   Disconnect wiring harness

   Carefully depress the locking tab and disconnect the electrical wiring harness from the switch.

4. 4

   Remove faulty switch

   Unbolt or unclip the faulty PTO brake switch from its mounting bracket.

5. 5

   Install new switch

   Install the new PTO brake switch into the bracket and secure it.

6. 6

   Reconnect wiring harness

   Reconnect the electrical harness, ensuring the weather-pack connector clicks firmly into place.

7. 7

   Reconnect battery

   Reconnect the battery and turn on the ignition.

8. 8

   Clear fault codes

   Clear the stored fault codes from the ACM using the tractor's diagnostic menu or a service tool.

9. 9

   Test PTO operation

   Test the PTO engagement and disengagement to verify the PTO brake functions correctly and the fault code does not return.