Case IH 518583-03 - UCM – UCM: Brake assisted steering pressure sensor voltage high

The control module is detecting that the electrical voltage signal returning from the brake-assisted steering pressure sensor is higher than the maximum allowable range.

• MAGNUM AFS Connect
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Magnum 400

1. 1

   Locate the brake-assisted steering isolation pressure sensor and inspect the 3-cavity electrical connector and wiring harness for physical damage, corrosion, or loose pins.

2. 2

   Disconnect the sensor and use a multimeter to verify the ground circuit. An open ground wire is the most common cause of a 'voltage high' code because it prevents the sensor from pulling the reference voltage down.

3. 3

   Test the signal wire between the sensor connector and the UCM to ensure it is not chafed and shorting against a 12V power source.

4. 4

   Inspect the multi-pin OEM connectors at the UCM for moisture intrusion or bent pins that could disrupt the sensor's signal processing.

1. 1

   Power down machine

   Turn off the tractor, remove the key, and disconnect the battery to protect the UCM and prevent accidental shorts during repair.

2. 2

   Disconnect sensor

   Locate the brake-assisted steering isolation pressure sensor on the hydraulic steering/brake valve block. Unplug the 3-cavity female electrical connector.

3. 3

   Repair wiring

   If the diagnostic checks revealed a broken ground or shorted wire, splice and repair the wiring harness using OEM-approved sealed terminals (e.g., 0.75 - 0.80mm gold female terminals).

4. 4

   Replace sensor

   If the wiring tests perfectly, the sensor has failed internally. Unthread the old pressure sensor from the hydraulic block, ensuring no dirt enters the hydraulic system. Install the new sensor and torque to OEM specifications.

5. 5

   Reassemble and clear codes

   Reconnect the 3-cavity electrical connector. Reconnect the battery. Use a compatible diagnostic tool (such as the Case IH EST or Jaltest commercial vehicle tool) to clear the active/pending 518583-03 fault code from the UCM's memory.

6. 6

   Test operation

   Start the tractor and engage the brake-assisted steering system (often programmed via the AFS Pro 1200 display for headland turns) to verify the code does not return.