Case IH 518395-06 - UCM – UCM: Pneumatic Trailer Brake Solenoid Circuit Current High

Indicates an electrical fault in the Pneumatic Trailer Brake Solenoid circuit. The controller is detecting an excessive current draw, usually caused by a short to ground in the wiring harness or an internally shorted solenoid coil.

• MAGNUM AFS Connect
• Magnum 340
• Magnum 400
• Puma 125
• Puma 150
• Puma 165
• Puma 170
• Puma 180
• Puma 195
• Puma 200
• Puma 210
• Puma 225
• Puma 230
• Maxxum 100
• Maxxum 110
• Maxxum 115
• Maxxum 120
• Maxxum 125
• Maxxum 140
• Optum 300 CVT
• Farmlift 742

1. 1

   Locate the Pneumatic Trailer Brake Solenoid (connector X431 or X318) at the rear of the tractor, either behind the cab or near the rear axle.

2. 2

   Inspect the wiring harness between the UCM and the solenoid, specifically looking at Pin 1 (Signal Wire, often Brown 8000) and Pin 2 (Ground Wire, often Black 57).

3. 3

   Use a multimeter to test for a short to ground on the signal wire (Brown 8000) between the UCM and the solenoid connector.

4. 4

   Disconnect the solenoid and measure the resistance across its pins to test the solenoid coil. A resistance near zero indicates an internal short.

1. 1

   Safely park the tractor on level ground, engage the parking brake, and turn off the engine.

   Ensure the machine is secure before beginning work.

2. 2

   Relieve any residual air pressure from the pneumatic trailer brake system to prevent injury.

   Depressurize the system safely.

3. 3

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

   Find the assembly to begin inspection and repair.

4. 4

   Disconnect the electrical connector (X431/X318) from the solenoid.

   Inspect the connector for moisture, corrosion, or melted pins which could cause a short.

5. 5

   If the wiring harness is damaged, repair the affected section.

   Specifically repair wires 8000 and 57 using appropriate weather-pack terminals.

6. 6

   If the solenoid coil failed the resistance test, unbolt the faulty pneumatic trailer brake solenoid valve from the air brake control block.

   Remove the internally shorted solenoid.

7. 7

   Install the replacement solenoid valve.

   Ensure any O-rings or seals are properly seated during installation.

8. 8

   Reconnect the electrical harness.

   Secure the connection to the new solenoid.

9. 9

   Power on the tractor and use the diagnostic display or service tool to clear the UCM fault codes.

   Test the trailer brake operation to verify the repair was successful.