Case IH 518588-02 - UCM – UCM: Brake assisted steering wheel speed disagreement

This fault indicates that the actual rotational speed of the inner wheel or track during a turn does not match the expected speed calculated by the system. The Brake Assisted Steering (BAS) system automatically applies the brake to the inside rear track or wheel during headland turns to reduce the turning radius. If the system commands the brake to apply but the wheel speed sensor detects that the wheel is not slowing down as expected (or vice versa), this disagreement code is logged.

• MAGNUM AFS Connect
• Magnum 280
• Magnum 310
• Magnum 325
• Magnum 340
• Magnum 380
• Magnum 400

1. 1

   Inspect the wheel speed sensors (left and right rear axles/track drives) for physical damage, heavy mud/debris buildup, or loose mounting brackets.

2. 2

   Inspect the Brake-Assisted Steering wiring harness and the jumper harnesses for chafing, pinched wires, or corrosion at the connectors.

3. 3

   Verify the steering angle sensor is reading correctly on the AFS Pro 1200 display. If the tractor doesn't know the exact steering angle, it cannot accurately calculate the expected inner wheel speed.

4. 4

   Test the BAS PWM solenoid valves (Left Hand and Right Hand). A standard 12V DC BAS solenoid should test at approximately 7.3 Ohms of resistance.

5. 5

   Ensure the service brakes are functioning normally. If the brake discs are worn or hydraulic pressure to the BAS valve block is insufficient, the brake will not physically slow the wheel down when commanded.

1. 1

   If replacing a BAS Solenoid / Coil: Park the tractor on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Relieve hydraulic pressure in the braking and steering circuits by pumping the brake pedals several times.

3. 3

   Locate the PTO/Differential/BAS valve block at the rear of the tractor.

4. 4

   Disconnect the electrical connector from the suspect BAS PWM solenoid.

5. 5

   Remove the solenoid retaining cover/nut.

6. 6

   Slide the faulty solenoid coil off the valve cartridge.

   If the cartridge itself is leaking or stuck, unthread the cartridge from the valve block and replace the O-rings or the entire cartridge.

7. 7

   Install the new solenoid coil, secure the retaining nut, and reconnect the harness.

8. 8

   If replacing a Wheel Speed Sensor: Locate the speed sensor on the affected rear axle housing or track drive hub.

9. 9

   Disconnect the sensor's electrical connector.

10. 10

    Remove the retaining bolt and carefully pull the sensor straight out of the housing.

11. 11

    Lubricate the O-ring on the new sensor with clean hydraulic oil and press it into the port.

12. 12

    Install the retaining bolt and torque to OEM specifications. Reconnect the harness.

13. 13

    Clear the fault codes from the UCM using the dealer Electronic Service Tool (EST) or the in-cab display.

14. 14

    Test drive the tractor and perform tight headland turns to verify the Brake Assisted Steering engages smoothly without logging the code.