Case IH 518395-05 - UCM – UCM: Pneumatic trailer brake solenoid current low

A "current low" or "current below normal" condition on a solenoid circuit indicates an open circuit, meaning the electrical path is broken and preventing current from flowing. The underlying cause is typically a disconnected harness plug, a broken or chafed wire, or a burnt-out (internally open) solenoid coil.

• MAGNUM AFS Connect
• Magnum 340
• Magnum 400
• Puma 125
• Puma 140
• Puma 155
• Puma 165
• Puma 170
• Puma 180
• Puma 195
• Puma 200
• Puma 230
• Maxxum 100
• Maxxum 110
• Maxxum 115
• Maxxum 120
• Maxxum 125
• Maxxum 140
• Optum 270
• Optum 300
• Farmall 85C
• Farmall 95C
• Farmall 105C

1. 1

   Locate the pneumatic trailer brake solenoid and inspect the electrical connector for looseness, corrosion, or pushed-out pins

2. 2

   Trace the wiring harness (circuit 8000 / 8000X and ground 57 / 57EK) back to the UCM to check for breaks, chafing, or pinched wires

3. 3

   Disconnect the solenoid connector and use a multimeter to measure the resistance across the solenoid coil pins (infinite resistance indicates a broken internal coil)

1. 1

   Park the tractor on a level surface, engage the parking brake, turn off the engine, and disconnect the negative battery terminal.

   Ensure the machine is safe to work on before beginning repairs.

2. 2

   Locate the pneumatic trailer brake control valve assembly at the rear of the tractor.

   This is where the faulty solenoid is mounted.

3. 3

   Disconnect the electrical harness connector from the faulty trailer brake solenoid.

   Prepare the solenoid for wiring repair or replacement.

4. 4

   If the diagnostic tests revealed a wiring issue, repair the broken wire in the harness or replace the damaged connector terminal.

   Address any open circuits found in the harness.

5. 5

   If the solenoid coil itself failed the resistance test, remove the retaining nut or screws securing the solenoid to the pneumatic valve block.

   Begin the removal process for the faulty solenoid.

6. 6

   Slide the old solenoid off the valve stem.

   Remove the defective part from the assembly.

7. 7

   Install the new OEM replacement solenoid and secure it with the retaining hardware.

   Ensure the new solenoid is properly seated and fastened.

8. 8

   Reconnect the electrical harness, ensuring the weather seal is intact and the connector clicks into place.

   Restore the electrical connection to the new solenoid.

9. 9

   Reconnect the battery.

   Restore power to the tractor.

10. 10

    Turn the key ON, clear the inactive fault codes from the UCM via the AFS Connect monitor or diagnostic tool, and test the pneumatic trailer brakes to ensure the code does not return.

    Verify the repair was successful and the system is functioning normally.