Case IH 519109-02 - UCM – UCM: Trailer brake test switch circuit fault

The system has detected an electrical circuit malfunction (such as an open circuit, short, or erratic signal) specifically tied to the rocker switch used to test the trailer brakes.

• MAGNUM AFS Connect
• Magnum AFS Connect series
• ActiveDrive 8 transmission tractors (Maxxum/Puma series)

1. 1

   Inspect the rocker switch on the C-pillar for physical damage, sticking, or debris preventing it from returning to its neutral position.

2. 2

   Access the back of the C-pillar panel and disconnect the switch. Use a multimeter to check for continuity across the switch terminals when toggled.

3. 3

   Inspect the wiring harness connecting the C-pillar switch panel to the UCM. Look for pinched wires, chafing, or corrosion at the connector pins that could cause an open or short circuit.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery or use the electronic battery isolator switch to prevent electrical shorts.

2. 2

   Access the Switch

   Carefully pry or unscrew the C-pillar control panel trim inside the cab to access the rear of the switch bank.

3. 3

   Remove the Faulty Switch

   Disconnect the wiring harness connector from the back of the trailer brake test switch. Depress the retention tabs on the sides of the rocker switch and push it outward through the front of the panel.

4. 4

   Install the New Switch

   Snap the new OEM rocker switch (Part # 51577458) into the panel until the tabs lock.

5. 5

   Reconnect

   Plug the wiring harness back into the switch. Reinstall the C-pillar trim panel.

6. 6

   Clear Codes

   Restore battery power, turn the ignition on, and use the tractor's AFS display or the Electronic Service Tool (EST) to clear the inactive 519109-02 fault code from the UCM. Test the switch to ensure the code does not return.