Case IH 518395-07 - UCM – UCM: High current in the pneumatic trailer brake solenoid

The control module is detecting an electrical current draw that exceeds the maximum allowable threshold, typically caused by a short circuit to ground in the wiring harness or an internally shorted solenoid coil.

• MAGNUM AFS Connect
• Magnum 400
• Puma 165
• Puma 180
• Puma 185 CVT
• Puma 195
• Puma 200
• Puma 210
• Puma 225 CVX
• Maxxum 110
• Maxxum 115
• Maxxum 120
• Maxxum 125 Multicontroller
• Maxxum 140
• Optum 270 CVT
• Optum 300 CVT
• T7 Series
• T7.210
• T7.230

1. 1

   Inspect wiring harness at Connector X431 (Pneumatic Trailer Brake Solenoid) for chafing, melting, or shorts to ground. Specifically check Wire 8000/8000X (signal) and Wire 57/57EK (ground).

2. 2

   Test solenoid internal resistance by unplugging it. A reading of near zero ohms indicates an internally shorted solenoid causing the high current draw.

3. 3

   Inspect the High Current Relay (12V, 190A) associated with the system for melted contacts.

4. 4

   Check the UCM power supply fuses (Fuses 1 through 10, typically 5A) to ensure the short hasn't blown the circuit protection.

1. 1

   Depressurize

   Stop the engine and ensure all pressure is completely relieved from both the hydraulic and pneumatic circuits before removing any caps, covers, or valves.

2. 2

   Locate the Solenoid

   The pneumatic trailer brake solenoid is typically located on the right-hand side of the tractor by the rear axle, mounted on top of the remote valve assembly.

3. 3

   Remove Bracketry

   Remove the pneumatic trailer brake bracket bolt from the top of the valve assembly.

4. 4

   Dismount the Valve

   Loosen and remove the top two retaining nuts on the side of the remote valve (these also retain the trailer brake valve bracket). Undo and remove the remaining retaining nut at the lower part of the valve slice.

5. 5

   Replace Component

   Disconnect the X431 electrical connector. Remove the faulty solenoid valve slice and install the replacement unit.

6. 6

   Reassembly

   Re-secure the retaining nuts and bracket bolts, reconnect the wiring harness, and test the tractor's braking system to ensure the high current fault is cleared.