Case IH 518392-05 - UCM – UCM: Secondary steering bypass solenoid current low

The UCM is detecting an electrical current draw that is below the minimum expected threshold when it commands the secondary steering bypass solenoid to activate. This typically points to an open circuit caused by a disconnected wiring harness, a broken wire, corroded connector pins, or an internal failure (open coil) within the solenoid itself.

• MAGNUM AFS Connect
• Magnum 400 AFS Connect
• Magnum 235
• Magnum 250
• Magnum 260
• Magnum 280
• Magnum 290
• Magnum 310
• Magnum 315
• Magnum 340
• Magnum 370
• Magnum 380

1. 1

   Visual Inspection: Locate the secondary steering bypass solenoid on the hydraulic steering valve block. Inspect the electrical connector for disconnected plugs, pushed-out pins, moisture ingress, or corrosion.

2. 2

   Wiring Harness Continuity: Disconnect the harness at the solenoid and at the UCM. Use a multimeter to check for continuity on both the power and ground wires. Check for any physical damage or chafing along the harness routing.

3. 3

   Solenoid Coil Resistance Test: Measure the resistance across the pins of the secondary steering bypass solenoid itself. If the multimeter reads 'OL' (Open Loop) or an unusually high resistance, the internal coil has failed.

4. 4

   Voltage Check: Turn the key to the ON position and verify that the UCM is sending the proper reference voltage to the solenoid connector when the secondary steering system is engaged or tested via the diagnostic display.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the battery ground cable to prevent electrical spikes during repair.

2. 2

   Access the Valve

   Clean the area around the secondary steering hydraulic block to prevent dirt from entering the hydraulic system.

3. 3

   Address Wiring

   If the diagnostic checks revealed a broken wire or corroded connector, repair the wiring harness using OEM-approved weatherproof splice kits or replace the connector pigtail.

4. 4

   Replace the Solenoid

   If the solenoid coil tested open: Disconnect the electrical connector from the solenoid. Remove the retaining nut or bolts holding the solenoid coil to the valve stem. Slide the old solenoid off the valve cartridge. (If the entire valve cartridge is faulty, depressurize the hydraulic system first, then unthread the cartridge from the manifold). Install the new solenoid coil and tighten the retaining nut to the manufacturer's torque specification.

5. 5

   Reassembly and Testing

   Reconnect the electrical plug and the battery. Turn the key on, navigate to the tractor's AFS Connect diagnostic display, and clear the UCM fault codes.

6. 6

   Verification

   Start the tractor and perform a steering system function test to ensure the secondary steering system engages properly and the 518392-05 code does not return.