Case IH 518587-03 - UCM – UCM: Brake assisted steering left wheel speed sensor voltage high

The control module is receiving a voltage signal from the left front wheel speed sensor that exceeds the normal operating parameters. This condition is typically caused by a short to battery power (B+), a damaged wiring harness, or an internal failure within the sensor itself.

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

1. 1

   Visual Inspection: Locate the left wheel speed sensor on the front axle/wheel hub. Inspect the sensor for physical damage, heavy debris buildup, or moisture intrusion.

2. 2

   Harness Inspection: Trace the wiring harness from the left wheel speed sensor back to the UCM. Look for chafed wires, pinched harnesses, or exposed copper that could cause a short to a power source (B+).

3. 3

   Connector Check: Disconnect the sensor and inspect the electrical connector. Look for corrosion, bent pins, or water ingress, which can bridge circuits and cause high voltage readings.

4. 4

   Multimeter Testing: With the key ON, use a multimeter to check the voltage at the sensor connector. Verify that the ground circuit is intact and check if the signal wire is shorted to a 12V power source.

1. 1

   Prepare machine and disconnect battery

   Park the tractor on a level surface, engage the parking brake, and turn off the engine. Disconnect the battery to prevent electrical shorts during the repair.

2. 2

   Locate sensor

   Locate the left wheel speed sensor on the front axle assembly.

3. 3

   Disconnect connector

   Disconnect the electrical connector from the sensor.

4. 4

   Repair wiring harness

   If your diagnostic checks revealed a wiring issue (short to power), repair the damaged section of the harness or replace the affected harness segment.

5. 5

   Remove sensor mounting bolt

   If the wiring and connectors test good, the sensor itself has failed internally. Remove the mounting bolt securing the sensor to the hub/axle.

6. 6

   Remove old sensor and clean surface

   Remove the old sensor and thoroughly clean the mounting surface to ensure the new sensor seats at the correct depth.

7. 7

   Install new sensor

   Install the new wheel speed sensor and tighten the mounting bolt.

8. 8

   Reconnect connector

   Reconnect the electrical connector, ensuring it clicks into place and the harness is secured away from moving parts.

9. 9

   Reconnect battery

   Reconnect the battery.

10. 10

    Clear fault code

    Turn the key ON and use the AFS Connect Pro display or the CNH Electronic Service Tool (EST) to clear the inactive fault code.

11. 11

    Test drive

    Test drive the tractor to verify that the brake-assisted steering functions correctly and the fault code does not return.