Case IH 517710-04 - UCM – UCM: Service brake pedal latch switch circuit fault

The system detects an irregular voltage reading from the switch that monitors whether the left and right service brake pedals are physically latched together for road travel (often indicating voltage low or a general circuit failure).

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect
• Case IH Farmall
• Case IH Maxxum

1. 1

   Use On-Board Voltmeter Diagnostics (H9 Menu, Channel 3) to observe live readings while latching and unlatching the brake pedals (should read 81 unlatched, 30 latched)

2. 2

   Inspect switch S33 wiring harness, inline connector X6, and keypad connector X7 for corrosion, pushed pins, or moisture

3. 3

   Verify sensor supply voltages at the UCM/controller pins (check for stable +5V, +8V, or +12V reference voltages)

1. 1

   Power Down

   Turn off the tractor and ensure all power is disconnected before servicing electrical components.

2. 2

   Access the Switch

   Locate the S33 brake pedal latch switch near the base of the service brake pedals in the cab.

3. 3

   Inspect the Mechanical Latch

   Ensure the mechanical pin that locks the two brake pedals together is not bent, binding, or failing to make physical contact with the switch actuator.

4. 4

   Test/Replace the Switch

   Disconnect the S33 switch connector. Test the switch for continuity when manually depressed. If it fails to close/open the circuit, remove the retaining hardware and install a new switch.

5. 5

   Reassemble and Clear Codes

   Reconnect the wiring harness, power the tractor on, and use the H9 diagnostic menu to verify the switch now toggles between states 81 and 30. Clear the 517710-04 code from the UCM memory.