Case IH 518658-02 - UCM – UCM: Right brake switch disagreement

The controller is receiving conflicting or illogical signals from the right brake pedal switch (e.g., both circuits simultaneously open or closed). This is usually caused by a failed internal switch contact, a wiring short/open circuit, or a mechanical issue preventing the pedal from fully returning to its resting position.

• MAGNUM AFS Connect
• Puma Series (150, 165, 185, 200, 240)
• Magnum Series (210, 250, 280, 340, 380)
• Maxxum Series (115, 125, 145, 150)
• Steiger / Quadtrac Series

1. 1

   Check the right brake pedal for physical obstructions, packed dirt, or a broken return spring that might be preventing the pedal from fully releasing.

2. 2

   Verify that the switch is securely mounted in its bracket and that the plunger is being fully depressed/released by the pedal arm.

3. 3

   Inspect the wiring harness and the connector at the right brake switch for rubbed wires, corrosion, or loose pins.

4. 4

   Disconnect the switch and use a multimeter to test the dual circuits. When the pedal is pressed, one circuit should close and the other should open. If they do not change state inversely, the switch is internally faulty.

5. 5

   Verify the CAN configuration in the Body Computer/UCM to ensure the module is communicating properly with the brake circuit.

1. 1

   Preparation

   Park the tractor on a level surface, apply the park brake, turn off the ignition, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Switch

   Access the brake pedal assembly under the cab console/dash. Locate the right brake switch mounted on the bracket above or behind the right brake pedal.

3. 3

   Removal

   Disconnect the electrical connector from the switch. Loosen the retaining nuts or clips holding the switch to the bracket and remove the faulty switch.

4. 4

   Installation

   Install the new OEM brake switch into the bracket.

5. 5

   Adjustment

   Thread the retaining nuts to adjust the switch clearance. Ensure the switch plunger is correctly actuated when the pedal is at rest and fully releases when the pedal is depressed (refer to the specific model's service manual for exact gap tolerances). Tighten the retaining nuts.

6. 6

   Reconnection

   Plug the electrical connector back into the switch and reconnect the battery.

7. 7

   Calibration/Clearing Codes

   Turn the ignition key to the ON position. Access the tractor's diagnostic menu (e.g., the "H" menu / H8 operation on Puma/Magnum models) or use the CNH Electronic Service Tool (EST) to clear the stored fault codes from the UCM's EEPROM.

8. 8

   Testing

   Test the brake pedals independently and locked together to ensure the fault does not return and that the brake lights operate correctly.