Case IH 518587-04 - UCM – UCM: Brake assisted steering left wheel speed sensor voltage low

FMI 04 specifically designates that the voltage is below normal or shorted to a low source. The system relies on active hall-effect wheel speed sensors to monitor wheel rotation frequency. When the control module detects that the voltage from the left wheel speed sensor has dropped below the acceptable operating threshold, it disables the brake-assisted steering feature (which normally helps reduce the turning radius by automatically applying the internal wet multi-disc brakes during headland turns) and logs this critical fault.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series (Models 250, 280, 310, 340, 380, and 400)
• Case IH Magnum Rowtrac AFS Connect Series

1. 1

   Inspect the left wheel speed sensor (located on the front axle/wheel hub) and its wiring harness for physical damage, chafing, or a disconnected plug.

2. 2

   Check the sensor's power and ground wires for an open circuit or a short to ground (which triggers the -04 voltage low state).

3. 3

   Inspect the speed sensor target wheel (tone ring) for damage, warping, or debris buildup that could disrupt the hall-effect sensor's frequency reading.

4. 4

   Verify the connections at the Universal Control Module to ensure no pins are pushed back or corroded.

1. 1

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

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

2. 2

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

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

3. 3

   Disconnect the sensor's electrical connector. Inspect the pins for corrosion or moisture intrusion.

   Disconnect the sensor's electrical connector. Inspect the pins for corrosion or moisture intrusion.

4. 4

   Using a multimeter, verify that the UCM is sending the correct reference voltage (typically 5V) to the sensor harness.

   Using a multimeter, verify that the UCM is sending the correct reference voltage (typically 5V) to the sensor harness.

5. 5

   If the reference voltage is present but the sensor fails to return a signal, the sensor has failed internally and must be replaced.

   If the reference voltage is present but the sensor fails to return a signal, the sensor has failed internally and must be replaced.

6. 6

   Remove the mounting bolt securing the left wheel speed sensor and pull the sensor out of the hub.

   Remove the mounting bolt securing the left wheel speed sensor and pull the sensor out of the hub.

7. 7

   Clean the mounting surface and install the new OEM wheel speed sensor. Torque the mounting bolt to OEM specifications.

   Clean the mounting surface and install the new OEM wheel speed sensor. Torque the mounting bolt to OEM specifications.

8. 8

   Reconnect the wiring harness. If the harness itself was found to be chafed or shorted to the chassis, splice and repair the damaged section or replace the brake-assisted steering sub-harness.

   Reconnect the wiring harness. If the harness itself was found to be chafed or shorted to the chassis, splice and repair the damaged section or replace the brake-assisted steering sub-harness.

9. 9

   Turn the ignition on and use the AFS Pro 1200 display or the Electronic Service Tool (EST) to clear the UCM fault codes.

   Turn the ignition on and use the AFS Pro 1200 display or the Electronic Service Tool (EST) to clear the UCM fault codes.

10. 10

    Test drive the tractor above 2.0 m/s to verify the UCM detects the wheel speed input and the brake-assisted steering engages correctly without the code returning.

    Test drive the tractor above 2.0 m/s to verify the UCM detects the wheel speed input and the brake-assisted steering engages correctly without the code returning.